Effects Engines

Comprehensive guide to VirtualDJ's multiple effect systems, how they work, and practical usage patterns.

Companion docs: Effects Usage.md is the shorter mental-model overview; Native Effects.md is the effect-name catalog.

Overview

VirtualDJ provides multiple independent effect engines that serve different purposes:

Effect Engine	Purpose	Location	Number of Slots
ColorFX	Quick filter/effect control	Filter knob per deck	1 per deck (special slot)
Mix FX	Crossfader-linked transition effect	Mixer / supported skins	1 selected Mix FX
Deck FX	Standard deck effects	FX panel per deck	3-6 slots per deck
Master FX	Global effects on master output	Master panel	3-6 slots
Video FX	Video effects and transitions	Video panel	Multiple slots
Stems FX	Effects applied to individual stems	Stems pads, Pad FX, named stem slots	Shared routing plus stem-specific slots
Pad FX	Quick-trigger effects with presets	Pads pages	Temporary effect triggers

A useful state model is persistent rack versus volatile performance FX. FX1-FX6 behave like the persistent deck rack: they are meant to be selected, shown, saved, restored, and then triggered or adjusted. Pad FX and named stem FX slots behave more like volatile pad-owned performance state: pads can assign them on demand, they survive normal track changes/current-session use, and they eventually clear rather than becoming the performer's saved rack.

ColorFX (Filter Slot)

What is ColorFX?

ColorFX is VirtualDJ's special effect slot integrated with the filter knob on each deck. It provides one-knob control for quick effects that work well with a single parameter.

Key Characteristics

One knob control: Designed for filter knobs on mixers
Pre-fader only: ColorFX is integrated with the EQ engine and always processes pre-fader
Curated effect list: Only effects designated as "ColorFX-compatible" appear in the selection menu
Center position: Knob at 50% (12 o'clock) = no effect, move left/right to apply

ColorFX vs Regular Filter

Starting with VirtualDJ 8.4+ builds, the traditional filter and ColorFX system were unified:

Filter is now a ColorFX effect (the default)
Use filter_selectcolorfx to choose different ColorFX
The knob action filter automatically works with whatever ColorFX is selected
Filter resonance can be adjusted via filterDefaultResonance option or filter_resonance action

Available ColorFX Effects

Common ColorFX-compatible effects include:

Filter (High-pass/Low-pass with resonance)
Echo
Flanger
Phaser
Noise
Pan
Wahwah
And others marked as ColorFX-compatible

VDJScript Commands

Select a ColorFX:

filter_selectcolorfx 'echo'
filter_selectcolorfx 'flanger'

Control the ColorFX knob:

filter                          # Main filter/colorFX control
filter 50%                      # Reset to center (no effect)
filter 75%                      # Set to specific position
filter_resonance 50%            # Adjust filter resonance

Activate/deactivate ColorFX:

effect_active 'colorfx'         # Toggle on/off
effect_active 'colorfx' on      # Turn on
effect_active 'colorfx' off     # Turn off

Show ColorFX GUI:

effect_show_gui 'colorfx'       # Open effect parameters window

Get ColorFX label:

filter_label                    # Returns name of selected ColorFX

Practical Usage

Basic filter control:

<slider action="filter" frommiddle="true">
  <pos x="100" y="100" />
  <size width="60" height="60" />
</slider>

Button to select and activate:

<button
  action="effect_active 'colorfx' & filter 50% & effect_show_gui 'colorfx'"
  rightclick="filter_selectcolorfx"
>
  <text action="filter_label" />
</button>

Important Notes

ColorFX is always pre-fader (cannot be changed to post-fader)
Only one ColorFX can be active per deck at a time
Some effects work better as ColorFX than others (check by testing parameter response)
Filter effect has special integration and may behave differently than other ColorFX

Mix FX (Crossfader-Linked FX)

What is Mix FX?

Mix FX is a transition-oriented effect path tied to crossfader movement. Official docs expose it through the effect_mixfx* verb family, and VirtualDJ forum context describes it as applying an effect to both decks with strength linked to the crossfader.

This is not the same engine as ColorFX, Deck FX slots, or Master FX:

ColorFX is per-deck and driven by the deck filter amount.
Deck FX is slot-based and driven by effect_select, effect_active, and effect_slider.
Master FX is applied to the master output.
Mix FX selects a transition effect associated with crossfader movement.

VDJScript Commands

Select the Mix FX:

effect_mixfx_select 'filter'
effect_mixfx_select 'echo'
effect_mixfx_select 'loop roll'
effect_mixfx_select 'reverb'
effect_mixfx_select 'noise'

Toggle Mix FX on/off:

effect_mixfx_activate
effect_mixfx_activate ? on : off

Select and activate:

effect_mixfx_select 'echo' & effect_mixfx_activate

Published skin note: the Denon Prime 4 Deluxe skin uses the reverse order:

<panel
  action="effect_mixfx_activate &amp; effect_mixfx_select 'FILTER'"
  query="effect_mixfx_select 'FILTER' ? effect_mixfx_activate"/>

Current local testing on VirtualDJ 8.5.9307 / 850.9336.mac.2224 confirmed direct and indirect selected-state queries in pad XML query/color, skin button query, and skin visibility. Keep the select-then-activate action order in examples because it is clearer, even though published skins sometimes use the reverse order.

Querying the Selected Mix FX

The no-parameter form can be used as a value-returning query:

effect_mixfx_select

For pad LED/color logic, older forum examples recommend comparing that returned value instead of relying on direct boolean parameter queries:

param_equal "`effect_mixfx_select`" "echo" ? blink 500ms : off

The Denon skin uses direct skin queries such as:

effect_mixfx_select 'FILTER' ? effect_mixfx_activate

Both direct and indirect selected-state forms work in current local pad and skin tests. The direct form is easier to read when the query is only "is this Mix FX selected"; the param_equal form remains useful when you need to compare the returned display value or document older-build-compatible examples.

Source Status

Official: current VDJScript verbs appendix lists effect_mixfx, effect_mixfx_activate, and effect_mixfx_select.
Official: DDJ-FLX2 hardware manual recommends effect_mixfx_select for assigning Mix FX in skins without native Mix FX controls.
Published skin: Denon Prime 4 Deluxe skin uses effect_mixfx_activate and effect_mixfx_select for named Mix FX buttons.
Community: forum examples document query caveats and param_equal comparison patterns.
Local test: direct and indirect effect_mixfx_select selected-state queries work in pad XML and skin contexts on VirtualDJ 8.5.9307 / 850.9336.mac.2224.

See Published Skin Findings for the provenance log and local test matrix.

Deck FX Slots (FX1, FX2, FX3, etc.)

What are Deck FX Slots?

Standard effect slots on each deck that provide full multi-parameter control with up to 6 parameters and 3 buttons per effect.

FX1-FX6 are the persistent deck rack. Skins and controller pages can show, trigger, and tweak whatever the performer has loaded there. A pad page can still select effects into these slots, but that should be treated as a deliberate rack-owning preset action because it changes persistent slot state.

Slot Configuration

VirtualDJ skins can display effects in different layouts:

Layout	Slots	Parameters per Effect
FX x1 (Single FX)	1 slot	Up to 6 parameters + 3 buttons
FX x3 (Multi FX)	3 slots	Up to 2 parameters per slot
FX x6 (Advanced)	6 slots	1-2 parameters per slot

Treat numbered deck FX slots 1-6 as the supported range. The current manual exposes an FX x6 deck view, hardware manuals describe six VirtualDJ FX slots, and the official effect_bank_save / effect_bank_load summaries explicitly cover deck FX slots 1 to 6. User-provided local observation on 2026-06-01 also found that FX1-FX6 keep their loaded effect across a VirtualDJ quit/reopen, while FX7 and higher keep their loaded effect during the current session/across track loads but reset after restart. Do not rely on numeric slots above 6 unless you have a local build-specific test and are comfortable with unsupported behavior.

VDJScript Commands

Effect Selection:

effect_select 1 'echo'          # Load Echo into slot 1
effect_select 2 'flanger'       # Load Flanger into slot 2
effect_select 3 'reverb'        # Load Reverb into slot 3
effect_select_multi 1 'reverb'  # Add Reverb to slot 1 without clearing earlier effects

Unlike padfx, effect_select does not accept inline effect parameter values. A persistent slot preset is an explicit chain:

effect_select 1 'cut' &
effect_slider 1 1 90% &
effect_slider 1 2 0.5bt &
effect_slider 1 3 50% &
effect_active 1 on

This writes the selected effect and slider values into the persistent FX1-FX6 rack. It does not have Pad FX's automatic "return parameters when stopped" behavior.

Effect Activation:

effect_active 1                 # Toggle slot 1 on/off
effect_active 2 on              # Turn slot 2 on
effect_active 3 off             # Turn slot 3 off

Effect Parameters (Sliders):

effect_slider 1 1 50%           # Slot 1, parameter 1 = 50%
effect_slider 1 2 1bt           # Slot 1, parameter 2 = 1 beat
effect_slider 2 1               # Control slot 2, param 1 (pass-through from knob)

Effect Buttons:

effect_button 1 1               # Press button 1 on slot 1 effect
effect_button 1 2               # Press button 2 on slot 1 effect
effect_button 1 3               # Press button 3 on slot 1 effect

Effect GUI:

effect_show_gui 1               # Show full GUI for slot 1 effect

Selecting next/previous effect:

effect_select 1 +1              # Next effect in list for slot 1
effect_select 1 -1              # Previous effect in list for slot 1

Checking if Effects are Active

Query if effect slot is active:

effect_active 1 ? action_if_true : action_if_false

Example button with visual feedback:

<button action="effect_active 1">
  <pos x="100" y="100" />
  <size width="80" height="40" />
  <off color="#404040" />
  <on color="#00FF00" />
  <text text="FX1" />
</button>

LED indicator for effect active:

<led brightness="`effect_active 1`">
  <pos x="50" y="50" />
  <size width="20" height="20" />
  <off x="0" y="100" />
  <on x="20" y="100" />
</led>

Effect by Name (Convenience Shortcut)

You can reference effects by name instead of slot number:

effect_active 'echo'            # Activate Echo (wherever it is)
effect_slider 'echo' 1 75%      # Control Echo param 1 directly
effect_active 'reverb' on       # Turn on Reverb effect

This is valid VDJScript and can be the right choice for quick personal mappings or a deliberate "toggle Echo wherever Echo is" shortcut.

For reference pad pages and controller-style examples, prefer slot addressing when the pad needs reliable state. If the page respects the user's persistent FX rack, trigger/control the existing slot with effect_active, effect_slider, and effect_button without changing the loaded effect. If the page is a self-contained preset page, it may use effect_select to write its own effect into the slot; document that as rack-owning behavior.

Three reliable rack-owning pad designs:

Dedicated slot pads: Each pad owns one slot, such as Echo on slot 1 and Reverb on slot 2. Use this when several effects should be able to stay active together.
Shared slot preset pads: Many pads program one slot, often slot 1. Pressing a pad replaces the slot's current effect, applies a known parameter preset, and activates the slot. Use this when pads are an effect picker.
Multi-effect slot pads: Several pads intentionally share one slot but call effect_select_multi so earlier effect instances stay loaded/active. Use an effect-name argument in effect_active for pad state, for example effect_active 1 'echo out', so Echo Out and Reverb can light independently even though they share slot 1.

For LED/query state, avoid checking only effect_active 1 on a pad labeled with an effect name. If slot 1 is active with Reverb, a pad labeled Echo should not blink. Check get_effect_name <slot> first, then nest the slot active check:

get_effect_name 1 & param_lowercase & param_equal 'echo' ?
  effect_active 1 ? blink 500ms : off :
  off

For a dedicated off control, call the slot activation verb with off:

effect_active 1 off

For intentional multiple effects in the same slot, use effect_select_multi and query/toggle the named instance:

effect_select_multi 1 'echo out' & effect_active 1 'echo out'
effect_select_multi 1 'reverb' & effect_active 1 'reverb'

For same-pad toggles, check that the slot already contains the named effect, then nest the active check:

get_effect_name 1 & param_lowercase & param_equal 'echo' ?
  effect_active 1 ?
    effect_active 1 off :
    effect_slider 1 1 75% & effect_slider 1 2 50% & effect_active 1 on :
  effect_select 1 'Echo' & effect_slider 1 1 75% & effect_slider 1 2 50% & effect_active 1 on

Do not use bare effect_select 1 for a state check. In pad actions, it can open the effect selector. Use effect_select 1 'Echo' only when deliberately loading Echo into slot 1.

Official VDJScript documents && for query chains, where the query should return true only when both commands are true. That does not make it a good fit for complex pad action branches that also load effects, set sliders, and toggle state. Use nested conditionals for same-pad toggle actions, and keep && to simple query expressions you have verified in the target surface.

Effect Chaining

Effects process in the order they were activated:

effect_select 1 'filter' & effect_active 1 on       # First in chain
effect_select 2 'echo' & effect_active 2 on         # Processes after filter
effect_select 3 'reverb' & effect_active 3 on       # Processes last

Result: Signal → Filter → Echo → Reverb → Output

Practical Usage Patterns

Simple toggle button:

effect_active 1

Hold-to-use effect:

effect_active 1 on while_pressed

Effect with auto-reset:

effect_active 1 on & wait 4bt & effect_active 1 off

Select and activate in one action:

effect_select 1 'echo' & effect_active 1 on

Temporary effect (release to deactivate):

down ? effect_active 1 on : effect_active 1 off

Master FX

What is Master FX?

Effects applied to the master output after all decks are mixed together. Affects the entire audio output.

Targeting Master Deck

Use deck master to target master FX slots:

deck master effect_select 1 'reverb'
deck master effect_active 1
deck master effect_slider 1 1 50%

Master FX Use Cases

Room/venue simulation: Reverb on master for ambience
Overall compression/limiting: Master processing
Broadcast effects: Effects for live streams
Emergency effects: Quick transitions or drops

Practical Example

Master effect that stays active:

# In controller ONINIT or custom button:
deck master effect_select 2 'MyVSTEffect' & 
deck master effect_active 2 on

Temporary master effect:

<button action="deck master effect_active 1 on while_pressed">
  <text text="MASTER VERB" />
</button>

Video FX

What are Video FX?

Effects that modify, transform, or overlay video output.

Video FX Categories

Video Effects - Applied to video sources (Blur, Colorize, Spectral, etc.)
Video Transitions - Crossfade effects (Cube, Doors, Fade, etc.)
Video Transforms - Modifications (Shake, Strobe, Negative, etc.)
Video Overlays - Text, titles, karaoke, etc.
Video Sources - Camera, slideshow, shader inputs

VDJScript Commands

Select video effect:

deck master video_fx_select 'spectral'
video_fx_select 'blur'          # On current deck

Activate or clear video effects:

video_fx                       # Toggle selected video effect on current deck/context
deck master video_fx           # Toggle selected master video effect
video_fx_clear                 # Deactivate all video effects for this context

Control video effect parameters:

deck master video_fx_slider 1 50%
deck master video_fx_slider 2 75%
video_fx_button 1
get_videofx_name
get_video_fx_slider_label 1

Video transitions:

video_transition 1000ms         # Crossfade with 1 second transition
video_transition_select 'cube'  # Select Cube transition
video_transition 2000ms         # Run selected transition over 2 seconds
video_transition_slider 1 50%
get_videotrans_name

Check video availability:

is_video ? action_if_video : action_if_audio_only

Practical Usage

Map video FX to filter knobs:

# Left filter = parameter 1, Right filter = parameter 2
device_side left ? deck master video_fx_slider 1 : deck master video_fx_slider 2

Built-in skin-style video FX panel:

<panel class="fxdrop_shorter"
       action1="video_fx"
       action2="video_fx_select"
       textaction="get_videofx_name &amp; param_uppercase"/>
<slider action="video_fx_slider 1"
        dblclick="video_fx_slider_reset 1"
        disabled="not effect_has_slider 'video' 1"/>

Built-in desktop skins use the same pattern for deck video FX and deck master video_fx... for master video FX. Use effect_has_slider 'video' <n> and get_video_fx_slider_label <n> to keep controls tied to the selected plugin's actual capabilities.

Source: Official, Built-in skin

Stems FX

What is Stems FX?

Effects applied to individual stems (Vocal, Melody, Bass, Drums, etc.) rather than the entire track.

How Stems FX Works

VirtualDJ exposes three related Stems FX patterns:

Shared FX-rack routing - effect_stems <stem> tells the normal deck FX rack which stem(s) to process.
Named stem FX slots - stem names such as vocals, bass, instru, rhythm, melody, hihat, and kick can be used as slot targets for effect_* actions, separate from numeric slots 1/2/3.
Pad FX stem targets - padfx ... 'stemfx:<stem>' triggers a pad effect on a stem without changing the normal rack routing.

The named slot model is easy to miss. In official forum guidance, Adion described vocals as its own slot, separate from slots 1/2/3, and usable with the broader effect_* action family.

Stem Selection Options

Vocal - Lead vocals only
Melody - Instruments and harmonies (Instru + Bass)
Rhythm - Percussion (HiHat + Kick)
MeloRhythm - Everything except vocals
Acapella - Vocals only (alternative term)
Instrumental - Everything except vocals (alternative term)
Individual stems: Vocal, HiHat, Bass, Instru, Kick

VDJScript Commands

Shared FX-rack routing:

effect_stems 'vocal'            # Apply effects to vocals only
effect_stems 'melody'           # Apply effects to melody only
effect_stems 'rhythm'           # Apply effects to drums only
effect_stems 'melorhythm'       # Apply effects to everything except vocals
effect_stems off                # Disable stems FX (back to full track)

Check if Stems FX is active:

effect_stems ? action_if_active : action_if_not_active

Combine with regular effects:

effect_stems 'vocal' & effect_active 1 'echo'

Named stem FX slots:

effect_select 'vocals' 'Reverb'     # Load Reverb into the vocal stem FX slot
effect_active 'vocals'              # Toggle the vocal stem FX slot
effect_select_multi 'vocals' 'Echo Out' # Add Echo Out without clearing other vocal effects
effect_active 'vocals' 'Echo Out'   # Toggle/query the named effect in the vocal slot
effect_slider 'vocals' 1 50%        # Move parameter 1 for the vocal stem FX slot
effect_slider 'vocals' 'echo' 1 50% # Move Echo param 1 in the vocal slot
effect_show_gui 'vocals' 'Reverb'   # Show the vocal Reverb GUI
effect_show_gui 'rhythm' 'Beat Grid'

vocals is plural in the stem-slot examples. This differs from the effect_stems 'vocal' and padfx ... 'stemfx:vocal' target strings. Current known named stem FX slots are vocals, bass, instru, rhythm, melody, hihat, and kick. melovocal and melorhythm may exist, but need local testing before they are treated as confirmed. Do not assume aggregate names such as instrumental or acapella are valid named stem FX slots unless tested.

User-provided local observation on 2026-06-01 found that named stem FX slots keep their loaded effect during the current session and across track loads, but reset after a VirtualDJ restart. Treat this as loaded-effect selection behavior only; active state, slider values, and multi-effect contents still need a recorded build-specific persistence pass.

That restart boundary makes named stem FX slots a good fit for pad-assigned, stateful performance effects. They let a pad own a vocal/rhythm/bass effect choice without overwriting the persistent FX1-FX6 rack.

Pad XML selected-state pattern:

<pad name="REVERB - Vocals"
     color="stem_color 'vocal'"
     query="effect_select 'vocals' 'reverb' ? effect_active 'vocals' : off">
  effect_select 'vocals' 'Reverb' &amp; effect_active 'vocals'
</pad>

Unlike the normal numeric-slot reference examples, this uses effect_select <stem-slot> <effect-name> as the selected-effect check because that is the observed working stem-slot pad pattern.

Pad XML multi-effect vocal slot pattern:

<pad1 name="FX-VOCALS\nECHO OUT"
      color="stem_color 'vocal'"
      query="effect_active 'vocals' 'echo out'">
  effect_select_multi 'vocals' 'echo out' &amp; effect_active 'vocals' 'echo out'
</pad1>
<pad2 name="FX-VOCALS\nREVERB"
      color="stem_color 'vocal'"
      query="effect_active 'vocals' 'reverb'">
  effect_select_multi 'vocals' 'reverb' &amp; effect_active 'vocals' 'reverb'
</pad2>

Both pads address the vocals stem FX slot, but the query/action includes the effect name. They can therefore light independently while both effects play through the same vocal slot. This is not the padfx ... 'stemfx:vocal' path; it is the regular effect_* stem-slot path with effect_select_multi.

The full list of accepted named stem FX slots is not published in the official appendix, so keep new target strings tied to local tests or forum evidence.

Stems FX from GUI

In the FX dropdown menu, toggle Stems FX mode:

Vocal button - Apply effects to vocals
Melody button - Apply effects to melody
Rhythm button - Apply effects to rhythm

When enabled, a small "S" icon appears next to effects indicating Stems FX mode.

Stems FX Pad Page

The Stems FX pad page provides quick access:

StemsFX Toggle - Cycles through Vocal/Melody/Rhythm/Off
Standard FX Pads - Trigger effects with StemsFX mode active

Practical Usage

Vocal-only echo out:

effect_stems 'vocal' & 
effect_active 'echo out' & 
wait 4bt & 
mute_stem 'vocal'

Instrument beatgrid effect:

effect_stems 'melorhythm' & 
effect_active 'beatgrid'

Toggle stems FX on/off:

<button
  action="toggle '$stemfx' & 
                var '$stemfx' ? effect_stems 'vocal' : effect_stems off"
>
  <text text="STEMS FX" />
</button>

Limitations and Notes

Pre-fader recommended: Stems FX works best with fxProcessing set to pre-fader
Some hardware incompatible: Controllers with hardware FX sends may not support Stems FX properly
ColorFX/stems behavior: Older forum guidance and local findings have been build-sensitive; test exact ColorFX-plus-stems behavior before relying on it
Reset options: Use resetStemsOnLoad and resetFXOnLoad options to auto-reset
Slot spelling: The vocal named stem FX slot is vocals, while the official padfx target is stemfx:vocal
Aggregate names: melovocal and melorhythm may exist as named stem FX slots, but need testing; instrumental and acapella are useful stem concepts but are not confirmed as named stem FX slots

Source Status

Official: VDJScript appendix documents effect_stems, effect_arm_stem, and padfx ... 'stemfx:stemname'.
Official forum: Adion documented effect_show_gui "rhythm" "Beat Grid" and said the same syntax can be used with other effect_* actions; he also described vocals as a separate effect slot.
Community: moderator examples use effect_show_gui vocals echo & padfx echo 'stemfx:vocal' to inspect a vocal padfx mapping.
Local test: vocal Reverb pad pattern with effect_select 'vocals' 'reverb' ? effect_active 'vocals'; user-provided multi-effect vocal pad pattern with effect_select_multi 'vocals' 'echo out' and effect_select_multi 'vocals' 'reverb' (build not recorded); user-provided restart-persistence observation that named stem FX slots reset their loaded effect after restart; current named slot list in local notes is vocals, bass, instru, rhythm, melody, hihat, and kick.

Pad FX

What is Pad FX?

Quick-trigger effects with pre-configured parameters, designed for single-button effect execution.

Pad FX Characteristics

Preset parameters: Effects are called with specific parameter values
Temporary by design: Intended to trigger and release, not save settings
Independent from slots: Can run alongside regular FX slots
Shared by effect/target identity: padfx 'reverb' ... 'stemfx:vocal' is not a private instance owned by the pad that called it
Volatile pad-owned state: Good when the pad should assign its own effect without rewriting FX1-FX6
Perfect for performance: Quick creative effects without knob adjustment

VDJScript Commands

Basic Pad FX:

padfx 'echo' 50% 1bt            # Echo at 50% strength, 1 beat length
padfx 'beatgrid'                # Trigger beatgrid effect
padfx 'flanger' 75% 2bt         # Flanger at 75%, 2 beat speed

Single Pad FX (one-shot):

padfx_single 'echo out' 80% 1bt

Pad FX with Stems:

padfx 'echo' 50% 1bt 'stemfx:vocal'
padfx 'reverb' 75% 'stemfx:melorhythm'
padfx 'echo out' 85% 70% 62.5% 20% 'stemfx:vocal'
padfx 'echo out' 80% 1bt 25% 75% 'stemfx:vocal'

Official padfx stem modifiers:

padfx 'echo out' 80% 'solostem:vocal'   # Only let vocal be audible during the effect
padfx 'echo out' 'mutestem:rhythm'      # Mute rhythm during the effect
padfx 'reverb' 'stemfx:vocal'           # Apply effect only to vocal

Official padfx stem names are Vocal, HiHat, Bass, Instru, Kick, Melody, Rhythm, MeloVocal, and MeloRhythm. Existing local pad pages normally use lowercase strings.

Full Pad FX syntax:

padfx 'effectname' param1 param2 param3 param4 'stemfx:stemname'

This compact "effect plus parameter list plus optional stem/switch modifier" form is specific to Pad FX. For regular persistent slot FX, the closest equivalent is an explicit effect_select / effect_slider / effect_button / effect_active chain, and that chain changes the rack state until something else changes it.

Pad FX Parameter Order

Parameters depend on the effect. Common patterns:

Echo:

padfx 'echo' strength% length_beats feedback% wetdry%
padfx 'echo' 50% 1bt 65% 75%

Echo Out:

padfx 'echo out' strength% length_beats
padfx 'echo out' 80% 1bt

Beatgrid:

padfx 'beatgrid'                # No parameters needed

Vinyl Brake:

padfx 'vinylbrake' multiplier length_beats echo% repeat%
padfx 'vinylbrake' 1bt 50% 50% 0%

Working Pad FX Parameter Examples

Treat these as working examples, not a complete effect-parameter specification. padfx arguments are effect-specific, and VirtualDJ does not publish a full native parameter map.

Effect	Working form	Source
Cut	`padfx 'cut' 50% 0.5bt`	`Local test`: `examples/Pads/PUSH FX.xml`
Cut	`padfx 'cut' 40% 1bt`	`Local test`: `examples/Pads/PUSH FX.xml`
Flanger	`padfx 'flanger' 70% 1bt`	`Local test`: `examples/Pads/PUSH FX.xml`
BeatGrid	`padfx 'beatgrid'`	`Local test`: `examples/Pads/PUSH FX.xml`
Echo on vocal stem	`padfx 'echo' 50% 1bt 65% 75% 'stemfx:vocal'`	`Local test`: `examples/Pads/PUSH FX.xml`
Reverb on vocal stem	`padfx 'reverb' 55% 2bt 'stemfx:vocal'`	`Local test`: `examples/Pads/PUSH FX.xml`
Echo Out on vocal stem	`padfx_single 'echo out' 80% 1bt 'stemfx:vocal'`	`Local test`: `examples/Pads/PUSH FX.xml`
Echo Out on vocal stem	`padfx "echo out" 80% 1bt "stemfx:vocal"`	`Built-in pad page`: `pads_stems+fx.xml`
Reverb on vocal stem	`padfx "Reverb" 80% "stemfx:vocal"`	`Built-in pad page`: `pads_stems+fx.xml`
BeatGrid on instrumental/melorhythm stem	`padfx "Beat Grid" "stemfx:MeloRhythm"`	`Built-in pad page`: `pads_stems+fx.xml`

The local PUSH FX page clears temporary pad effects with:

effect_disable_all 'padfx'

That is useful for separate reset/cleanup controls on momentary performance pages that track their own pad state with variables. User-provided testing found that chaining effect_disable_all 'padfx' immediately before new padfx calls in the same pad action can prevent the new pad FX from activating or lighting, while the same chained padfx calls work when the inline clear is removed. Treat effect_disable_all 'padfx' as a cleanup command, not as a deterministic initializer for a new pad-FX chain.

padfx is deterministic about the values passed at the moment it starts, but it does not appear to provide per-pad ownership. Another pad that calls the same effect and stem target, for example another padfx 'reverb' ... 'stemfx:vocal', can reuse or retune that shared pad-FX identity. Use padfx for volatile performance gestures. If the performer needs a restart-persistent rack or a visible stable chain, reserve numbered deck FX slots 1-6; if a pad writes those slots with effect_select, document that it owns/reprograms the rack.

Checking Pad FX Status

Pad FX don't have a built-in "active" query. Track status with variables:

# Set variable when activating
set 'padfx_active' 1 & padfx 'echo' 50% 1bt

# Check variable
var 'padfx_active' ? visual_feedback_on : visual_feedback_off

Show Pad FX GUI

effect_show_gui 'stemname' 'effectname'
effect_show_gui 'vocals' 'echo'
effect_show_gui 'rhythm' 'beatgrid'

For GUI calls, source examples use the stem-slot style (vocals) rather than the padfx modifier style (stemfx:vocal).

Practical Usage

Simple pad effect:

<button action="padfx 'echo out' 75% 1bt">
  <text text="ECHO OUT" />
</button>

Stems-specific pad effect:

<button
  action="effect_stems 'vocal' & 
                padfx_single 'echo out' 80% 1bt & 
                wait 4bt & 
                mute_stem 'vocal' & 
                effect_stems off"
>
  <text text="VOCAL OUT" />
</button>

Advanced stems + effect combo:

<!-- Mute melody, echo it out, then mute it -->
<button
  action="var 'stemsnfx' 1 ? 
                  toggle 'stemsnfx' & mute_stem 'melody' off : 
                  toggle 'stemsnfx' & 
                  effect_stems 'melody' & 
                  padfx_single 'echo out' 75% 1bt & 
                  wait 1bt & 
                  mute_stem 'melody' & 
                  effect_stems off"
>
</button>

Pre-Fader vs Post-Fader

What's the Difference?

Pre-fader: Effects process before volume faders and crossfader
Post-fader: Effects process after volume faders and crossfader

Signal Flow

Pre-fader:

Deck → Effects → EQ → Volume Fader → Crossfader → Master

Post-fader:

Deck → EQ → Volume Fader → Crossfader → Effects → Master

When to Use Each

Use Pre-fader when:

Effects should continue playing even when fader is down (echo tails)
Using effects with stems (Stems FX requires pre-fader)
Most creative DJ effects work

Use Post-fader when:

Effects should stop immediately when fader is down
Using effects during transitions
Hardware requires it (some mixers)

Setting FX Processing Mode

Global setting:

setting 'fxProcessing' 'pre-fader'
setting 'fxProcessing' 'post-fader'

Temporary change:

setting 'fxProcessing' 'post-fader' & 
padfx 'echo out' 1bt 50% & 
wait 5000ms & 
setting 'fxProcessing' 'pre-fader'

Option in Settings:

Settings → Audio → fxProcessing → Pre-fader / Post-fader

Important Notes

ColorFX is always pre-fader (cannot be changed)
Hardware effects: Some controllers have hardware post-fader sends
Stems FX: Works best in pre-fader mode
Default: Pre-fader is the default and most common setting

Effect Queries and Conditionals

Checking Effect Status

Is any effect active on slot:

effect_active 1 ? blink : off

Is specific effect active:

get_effect_name 1 & param_lowercase & param_equal 'echo' ?
  effect_active 1 ? action_if_echo_active : action_if_echo_loaded_off :
  action_if_other_effect_loaded

Are stems FX active:

effect_stems ? show_stems_indicator : hide_indicator

Multiple effect check:

effect_active 1 | effect_active 2 | effect_active 3 ? led_on : led_off

Visual Feedback Examples

Button color based on effect state:

<button action="effect_active 1">
  <size width="80" height="40" />
  <up color="#404040" radius="4" />
  <selected color="#00FF00" radius="4" />
  <text text="FX 1" />
</button>

LED indicator:

<visual source="`effect_active 1`" type="onoff">
  <pos x="100" y="50" />
  <size width="10" height="10" />
  <off color="black" />
  <on color="red" />
</visual>

Text showing effect name:

<textzone>
  <pos x="100" y="100" />
  <size width="200" height="30" />
  <text text="`get_effect_name 1`" />
</textzone>

Blink when effect active:

effect_active 1 & blink 500ms

Effect Introspection and Dynamic Controls

For generic FX panels, skins do not need to hardcode every slider and button. VirtualDJ exposes helpers that ask the selected plugin what it supports:

effect_has_slider 1 1              # Does slot 1 have slider/parameter 1?
effect_slider 1 1                  # Move/query slot 1 slider 1
effect_slider_reset 1 1            # Reset slot 1 slider 1 to default
get_effect_slider_default 1 1 0.5  # Slot form: centre/default in a value context (skin frommiddle); see note. Text readback uses the effect-name form below.
get_effect_slider_label 1 1        # Display label for slot 1 slider 1
get_effect_slider_text 1 1         # Display formatted current value
effect_has_button 1                # Does the selected effect expose button 1?
effect_button 1                    # Press button 1 in single-FX layout
get_effect_button_shortname 1      # Compact label for button 1
get_effect_slider_count            # Number of sliders in the current context
get_effect_button_count            # Number of buttons in the current context

Helper reliability (Local test: VirtualDJ v2026-m b9482, Reference - FX Introspection Test.xml, deck FX slot 1, Backspin). These returns were read live and cross-checked against the effect's GUI:

Helper	Returns	Reliable?
`get_effect_name <slot>`	effect name (`Backspin`)	Yes — matches GUI
`get_effect_slider_count` / `get_effect_button_count`	slider/button count (`2` / `0`)	Yes
`effect_has_slider <slot> <n>` / `effect_has_button <n>`	on/off for each index	Yes — lit correctly per position
`get_effect_slider_text <slot> <n>`	formatted current value (`0%`, `4 bt`)	Yes — matches GUI value
`get_effect_slider_label_full` / `get_effect_slider_name`	full label (`Strength`, `Length`)	Yes — matches GUI label
`get_effect_slider_label` / `get_effect_slider_shortname`	short label (`STR`, `LEN`)	Yes — short form
`get_effect_slider_default '<effect>' <fallback>`	normalized `0.5` for Backspin (fallback `1` overridden)	Yes — genuine default, readable as text
`get_effect_slider_default <slot> <index> <fallback>`	`off` in a `name=` text context	Value-context only — see note

get_effect_slider_default takes a target (an FX slot number, an effect name, or 'active' for the selected effect), an optional slider index, and a trailing fallback/centre value, and returns a normalized 0-1 default:

get_effect_slider_default '<effect>' <fallback> — the effect-name form. Confirmed by both a Local test (get_effect_slider_default 'Backspin' 1 → 0.5, i.e. a real default, not the 1 fallback) and shipped Built-in skin XML: the Broadcast video skin uses frommiddle="get_effect_slider_default 'active' 0.5" alongside effect_slider 'active' (examples/VideoSkins/Built-In/broadcast/broadcast.xml:241). The 0.5 there is the fallback, not a slider index.
get_effect_slider_default <slot> <index> <fallback> — the deck-skin form, used 300+ times inside <slider frommiddle="…"> (also a 2-arg <slot> <fallback> variant). It returned off when read in a pad name= text context, so treat it as value-context-only, not a text readback. It is not broken; the earlier "broken" note was a wrong-argument call (a slot number passed where the effect-name form expects a target name).

Guidance from the above:

For a GUI-matching parameter label use get_effect_slider_label_full (or get_effect_slider_name); for a compact label use get_effect_slider_label (or get_effect_slider_shortname). They are two distinct forms, not aliases.
For live values use get_effect_slider_text. Counts and effect_has_* are safe to drive dynamic panels.
To read a default as a value/number, use the effect-name form get_effect_slider_default '<effect>' <fallback> (or 'active' for the selected effect); for skin sliders, the slot form in frommiddle="get_effect_slider_default <slot> <index> <fallback>" positions the centre.
debug cannot print a computed value: it logs the literal backtick expression (same computed-argument behavior as loop/beatjump/phrase_sync). Read helper strings through a pad/skin name=/text= interpolation instead.

Per-effect parameter map (Local test: VirtualDJ v2026-m b9482, deck FX slot 1). Growing as effects are swept; absence of a row means "not yet recorded", not "no parameters".

Effect	Sliders (full / short — unit)	Buttons
Backspin	S1 `Strength` / `STR` (%), S2 `Length` / `LEN` (beats)	0
Flanger	S1 `Strength` / `STR` (`50%` reset), S2 `Speed` / `LEN` (`8 bt` reset), S3 `Feedback` / `FBCK` (`50%` reset), S4 `LFO Amp` / `LFO` (`50%` reset)	B1 `Tone` / `TONE`, B2 `Phase` / `PHASE`
Echo	S1 `Strength` / `STR` (`52%` reset), S2 `Length` / `LEN` (`1/2 bt` reset), S3 `Feedback` / `FB` (`52%` reset), S4 `Filter` / `FILT` (`OFF` reset), S5 `Lowpass` / `LP` (`20 Hz` reset), S6 `Highpass` / `HP` (`20000 Hz` reset)	B1 `Reverse` / `REV`, B2 `Freeze` / `FRZ`, B3 `Mute Source` / `MUTE`, B4 `Lock On Max` / `LCK`
Reverb	S1 `Strength` / `STR` (`50%` reset), S2 `Decay` / `DEC` (`50%` reset), S3 `Room Size` / `SIZE` (`50%` reset), S4 `Brightness` / `BRI` (`50.0%` reset)	B1 `Low Cut` / `LOW`, B2 `Hi Cut` / `HI`
Beat Grid	S1 `Slot` / `SLOT` (`Slot 1` reset)	B1 `Mode` / `>>`, B2 `Video` / `VIDEO`
Beat Brake	S1 `Strength` / `STR` (`50%` reset), S2 `Pattern` / `PAT` (`Pat 1` reset), S3 `Bars` / `BARS` (`2 bars` reset), S4 `HPF` / `HPF` (`Off` reset)	B1 `Quantize` / `QUANT`
BrakeStart	S1 `Length` / `LEN` (`2.76 s` reset)	B1 `Restart Play` / `RESTART`
Choppa	S1 `Strength` / `STR` (`100%` reset), S2 `Length` / `LEN` (`Pat 1` reset), S3 `Invert` / `INV` (`Off` reset)	B1 `Quantize` / `QUANT`
Cut	S1 `Strength` / `STR` (`52%` reset), S2 `Length` / `LEN` (`1/2 bt` reset), S3 `Duty` / `DUTY` (`50%` reset), S4 `Swing` / `SWING` (`0%` reset)	B1 `Low Cut` / `LOW`, B2 `High Cut` / `HIGH`, B3 `Mute Beats` / `INV`, B4 `Video` / `VIDEO`
Cyclone	S1 `Strength` / `STR` (`50%` reset), S2 `Length` / `LEN` (`1/2 bt` reset), S3 `Delay` / `DELAY` (`203 ms` reset)	0
Delay	S1 `Strength` / `STR` (`52%` reset), S2 `Length` / `LEN` (`1/2 bt` reset), S3 `Swing` / `SWING` (`0%` reset), S4 `LR Ratio` / `LR` (`0%` reset)	B1 `Low Cut` / `LC`, B2 `High Cut` / `HC`

For Flanger, get_effect_slider_count returned 4 and get_effect_button_count returned 2; the corresponding four slider pads and two button pads were the only positions reported by effect_has_*. The GUI labels matched the helper map, including the non-obvious Speed / LEN full/short pair. The fixture's by-name default pad was still hardcoded to Backspin, so its displayed 0.5 is not evidence for Flanger's normalized default.

For Echo, get_effect_slider_count returned 6 and get_effect_button_count returned 4; the corresponding positions matched the visible GUI controls. The GUI supplied the full labels for S2-S6 and B2-B4; the fixture directly confirmed S1 Strength / STR and B1 Reverse / REV. The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for Echo's normalized default.

For Reverb, get_effect_slider_count returned 4 and get_effect_button_count returned 2; all positions matched the visible GUI controls. The fixture directly confirmed S1 Strength / STR and B1 Low Cut / LOW; the GUI supplied the full labels for the remaining controls. The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for Reverb's normalized default.

For Beat Grid, get_effect_slider_count returned 1 and get_effect_button_count returned 2; all positions matched the visible GUI. S1 selects the displayed pattern slot and reset changed its readback from Slot 3 to Slot 1. B1 Mode corresponds to the GUI's SNGL / CONT mode control, and B2 is Video. The exact selector name includes a space: effect_select 1 'Beat Grid'; the fixture's earlier 'BeatGrid' call left the previous effect selected. The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for Beat Grid's normalized default.

For Beat Brake, get_effect_slider_count returned 4 and get_effect_button_count returned 1; the corresponding positions were the only ones reported by effect_has_*. The fixture directly confirmed S1 Strength / STR and B1 Quantize / QUANT; the GUI supplied the remaining full labels and matched the reset readbacks. The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for Beat Brake's normalized default.

For BrakeStart, get_effect_slider_count returned 1 and get_effect_button_count returned 1; both positions matched the visible GUI. The fixture and GUI agreed on S1 Length / LEN (2.76 s reset) and B1 Restart Play / RESTART. The selected effect name and popup both use BrakeStart, correcting the stale Break Start spelling in the native-effects catalog. The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for BrakeStart's normalized default.

For Choppa, get_effect_slider_count returned 3 and get_effect_button_count returned 1; all positions matched the visible GUI. The controls were S1 Strength / STR (100% reset), S2 Length / LEN (Pat 1 reset), S3 Invert / INV (Off reset), and B1 Quantize / QUANT. The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for Choppa's normalized default.

For Cut, get_effect_slider_count returned 4 and get_effect_button_count returned 4; all positions matched the visible GUI. The fixture directly confirmed S1 Strength / STR and B1 Low Cut / LOW; the GUI supplied the remaining full labels. The non-obvious B3 mapping is Mute Beats / INV. The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for Cut's normalized default.

For Cyclone, get_effect_slider_count returned 3 and get_effect_button_count returned 0; all positions matched the visible GUI. The controls were S1 Strength / STR (50% reset), S2 Length / LEN (1/2 bt reset), and S3 Delay / DELAY (203 ms reset). The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for Cyclone's normalized default.

For Delay, get_effect_slider_count returned 4 and get_effect_button_count returned 2; all positions matched the visible GUI. The controls were S1 Strength / STR (52% reset), S2 Length / LEN (1/2 bt reset), S3 Swing / SWING (0% reset), S4 LR Ratio / LR (0% reset), B1 Low Cut / LC, and B2 High Cut / HC. The fixture's by-name default pad remained hardcoded to Backspin, so its 0.5 is not evidence for Delay's normalized default.

Built-in desktop skins use this pattern for slot controls:

<slider action="effect_slider 1 1"
        dblclick="effect_slider_reset 1 1"
        disabled="not effect_has_slider 1 1"
        frommiddle="get_effect_slider_default 1 1 0.5"/>
<textzone>
  <text action="get_effect_slider_label 1 1"/>
</textzone>
<button action="effect_button 1"
        visibility="effect_has_button 1"
        textaction="get_effect_button_shortname 1"/>

Use the no-slot form in single-FX layouts where the selected plugin owns the current control bank:

<slider action="effect_slider 1"
        dblclick="effect_slider_reset 1"
        disabled="not effect_has_slider 1"
        frommiddle="get_effect_slider_default 1 0.5"/>
<textzone>
  <text action="get_effect_slider_label 1"/>
</textzone>

Video FX and transition panels use the same idea with special targets:

<slider action="video_fx_slider 1"
        dblclick="video_fx_slider_reset 1"
        disabled="not effect_has_slider 'video' 1"
        frommiddle="get_video_fx_slider_default 1 0.5"/>
<text action="get_video_fx_slider_label 1"/>

<slider action="video_transition_slider 1"
        dblclick="video_transition_slider_reset 1"
        disabled="not effect_has_slider 'transition' 1"
        frommiddle="get_effect_slider_default 'transition' 1 0.5"/>
<text action="get_effect_slider_label 'transition' 1"/>

This is the preferred way to build a reusable FX surface. Hardcoded parameter labels are fine for a known pad preset, but generic panels should follow the selected plugin's actual slider/button count and labels. Until the fixture logs more native effects, keep effect-specific labels in examples tied to the recorded effect/build, and leave missing counts or helper strings as unknown.

Source: Official, Built-in skin, Local test, Inference

Practical Effect Workflows

Workflow 1: Echo Out Transition

Gradually remove track with echo tail:

effect_stems off & 
effect_select 1 'echo out' & 
effect_slider 1 1 80% & 
effect_slider 1 2 1bt & 
effect_active 1 on & 
wait 4bt & 
volume 0% 2000ms

Workflow 2: Beatgrid Breakdown

Create a breakdown using beatgrid:

effect_select 1 'beatgrid' & 
effect_active 1 on & 
wait 16bt & 
effect_active 1 off

Workflow 3: Vocal Echo with Stems

Echo only the vocals:

effect_stems 'vocal' & 
padfx 'echo' 50% 1bt & 
wait 8bt & 
effect_stems off

Workflow 4: Build Up with Multiple Effects

Chain effects for a build-up:

# Start with light flanger
effect_select 1 'flanger' &
effect_slider 1 1 25% &
effect_active 1 on &

# Add echo
wait 8bt &
effect_select 2 'echo' &
effect_slider 2 1 50% &
effect_active 2 on &

# Add reverb
wait 8bt &
effect_select 3 'reverb' &
effect_active 3 on &

# Drop - remove all
wait 8bt &
effect_active 1 off &
effect_active 2 off &
effect_active 3 off

Workflow 5: Acapella Out with Reverb

Remove everything but vocals with reverb tail:

effect_stems 'vocal' & 
padfx 'reverb' 75% 4bt & 
wait 2bt & 
mute_stem 'vocal' & 
effect_stems off

Effect Lists and Organization

Creating Effect Lists

VirtualDJ allows organizing effects into custom lists for quick access.

Managing Effect Lists

Open Effects dropdown
Scroll to bottom
Click "More..." or "Manage..."
Audio Effects List Editor opens

List Editor Functions

Search bar: Find effects quickly
Current list: Switch between lists
Add/Remove: Build custom effect collections
New list: Create specialized collections
Delete list: Remove unwanted lists

Practical List Examples

"Quick FX" list:

Filter
Echo
Reverb
Beatgrid
Brake

"Build Up FX" list:

Flanger
Phaser
Echo
Reverb
Riser

"Stems FX" list:

Echo Out
Reverb
Beatgrid
Vinyl Brake

Advanced Effect Techniques

Effect Banks

VirtualDJ exposes built-in bank helpers for saving and loading the current deck FX slots. Prefer these when the goal is "store this FX rack and recall it later":

effect_bank_save 1
effect_bank_load 1

The official summary says banks cover deck FX slots 1-6. Treat bank contents as persistent rack-level snapshots. If a pad needs to guarantee Echo at 1 beat and Reverb at 40% by writing FX1-FX6, document that it is intentionally reprogramming the saved rack; otherwise leave bank/slot selection alone and only trigger or adjust the existing rack.

Use variables only for custom behavior the bank helpers do not model, such as remembering one slot name inside a larger macro:

set 'fx_return_slot1' `get_effect_name 1`
effect_select 1 `get_var 'fx_return_slot1'`

Source: Official, Inference

FX Layout, Lists, and Selectors

These helpers are UI/rack helpers rather than effect-processing engines:

effect_3slots_layout              # Toggle 1-slot / 3-slot FX panel layout
effect_select_popup 1             # Open/select from the slot 1 effect popup
effect_select_toggle 1 'Echo'     # Select effect while keeping activation continuity
effect_list 1 +1                  # Cycle effect list for slot/list context
effect_list_edit 1                # Open editor for an effect list
effect_clone                      # Clone FX slots from another deck

Built-in and SDK example skins use effect_3slots_layout for switching single-FX and multi-FX panels. Reference pad pages use effect_select_popup <slot> for parameter buttons that should open the native slot selector.

Use these to expose VirtualDJ's existing FX UI model. For deterministic pads, prefer explicit slot actions.

Source: Official, Built-in skin, Local test

Armed FX

The effect_arm_* family models hardware-style workflows: choose a target deck/path, choose an effect, choose participating slots, then activate or move the armed effect.

effect_arm_deck master
effect_arm_select 'Echo'
effect_arm_slot 1
effect_arm_active
effect_arm_slider 1 50%
effect_arm_beats 1

Use this family for controller mappings that already have an "armed FX" mental model. In skins and pad pages, direct slot actions are usually clearer:

deck master effect_select 1 'Echo' & deck master effect_active 1

Do not confuse effect_arm_stem Vocal with named stem FX slots such as vocals. effect_arm_stem selects stems for the special stems slot used by the armed/direct effect_* model; vocals is a separate named stem FX slot.

Source: Official, Inference

Release FX

Release FX uses a separate slider path from normal deck FX sliders:

effect_releaseslider 50%
effect_releaseslider_active 50%
is_releasefx ? on : off

Use effect_releaseslider_active when moving the release control should also activate the release effect. Use effect_slider / effect_slider_active for ordinary deck FX slots. Exact release-FX slot selection and plugin-specific behavior still needs a focused local fixture before this becomes a canonical pad pattern.

Source: Official

Status: Needs local test.

FX Send/Return

Send/return helpers are for hardware-style routing paths where effects are applied to a selected source rather than a normal deck slot:

effect_fxsendreturnenable
deck 1 effect_fxsendreturndeck
deck 2 effect_fxsendreturndeck_multi master
deck 2 effect_fxsendreturndeck_multi mic

Keep these out of ordinary pad-page examples unless the target controller or skin exposes an FX send/return workflow. The official appendix names the helpers, but local behavior depends on routing and hardware/software mixer context.

Source: Official

Status: Needs local test.

Plugin-Specific Commands

effect_command sends commands to the currently targeted effect/plugin. Built-in plugin UI XML for BeatGrid uses strings such as set 00, get 00, and cur 0:

<button action="effect_command 'set 00'"
        query="effect_command 'get 00'"/>
<visual source="effect_command 'cur 0'"/>

The same file also shows context-dependent shortcuts around the selected plugin:

<button action="effect_show_gui"/>
<button action="effect_dock_gui"/>
<button action="effect_active"/>
<text action="get_effect_title"/>
<button action="effect slider 1 +0.143"/>
<text format="`get_effect_slider_text 1` / 8"/>
<button action="effect_button 1 on"/>

This is useful evidence that a plugin UI can be a fixed bitmap control surface with hardcoded plugin commands, direct coordinate arithmetic such as x="4*20+9+3", and repeated controls without <define>, <deck>, or <panel> containers. It is not evidence for a universal effect_command language, a reusable generic FX rack, or the recommended structure for desktop/Remote skins. Generic skins should still prefer slot/target-qualified controls and introspection helpers such as effect_has_slider, get_effect_slider_label, and get_effect_button_shortname.

Source: Built-in skin (examples/Skins/Built-In/Plugin-UI/AFX_beatgrid.xml), Inference

Effect Presets with Parameters

Save effect + parameters:

# Preset: Heavy Echo
effect_select 1 'echo' & 
effect_slider 1 1 75% & 
effect_slider 1 2 2bt & 
effect_slider 1 3 80% & 
effect_active 1 on

# Preset: Light Reverb
effect_select 2 'reverb' & 
effect_slider 2 1 30% & 
effect_slider 2 2 50% & 
effect_active 2 on

Macro Effects

Combine multiple actions:

# "Drop" macro: Kill all effects, reset filter, cut bass momentarily
effect_active 1 off & 
effect_active 2 off & 
effect_active 3 off & 
filter 50% & 
eq_low 0% & 
wait 1bt & 
eq_low 100%

Effect Automation

Use repeat_start for automated effect patterns:

# Auto-toggle filter every 4 beats
repeat_start 'auto_filter' 4bt 0 & 
  filter `filter ? 75% : 25%`

# Stop automation
repeat_stop 'auto_filter'

Troubleshooting Common Issues

Effects Not Working

Check:

Effect is selected in slot: get_effect_name 1
Effect is activated: effect_active 1
Parameters are not at 0: effect_slider 1 1 50%
Pre/post-fader setting matches hardware
Audio routing is correct

Effects Sound Wrong

Check:

Parameter values are appropriate for the effect
Multiple effects aren't conflicting
Effect is suitable for the material (some effects work better on certain genres)
Stems separation quality (if using Stems FX)

Stems FX Issues

Check:

Stems are analyzed/prepared
fxProcessing is set to pre-fader
Hardware supports software effects (not hardware sends)
effect_stems is active: effect_stems ? on : off
Correct stem name is used (Vocal, Melody, Rhythm, etc.)

ColorFX Not Responding

Check:

Effect is ColorFX-compatible (not all effects are)
Using filter action, not effect_slider 'colorfx'
Filter knob is mapped correctly: filter with frommiddle="true"
Effect is actually selected: filter_selectcolorfx 'effectname'

Mix FX Not Responding

Check:

The skin or custom button exposes Mix FX activation: effect_mixfx_activate
The selected Mix FX is set with effect_mixfx_select '<name>'
Query logic is using a tested form for the current context:
- effect_mixfx_activate ? on : off for activation state
- param_equal "\effect_mixfx_select`" "" ? on : off` for selected-name comparisons until direct queries are locally verified
Crossfader movement is part of the intended behavior; Mix FX is not a normal static deck FX slot

Effect Parameters Not Changing

Check:

Correct slot number: effect_slider 1 1 vs effect_slider 2 1
Correct parameter number (1-6)
Value format matches parameter type (% for dry/wet, bt for beats, ms for time)
Effect GUI isn't overriding controller values

Quick Reference

Effect Commands Cheat Sheet

# SELECTION
effect_select 1 'echo'              # Select effect for slot 1
effect_select_multi 1 'reverb'      # Add effect to slot 1 without clearing earlier effects
effect_select 'vocals' 'reverb'     # Select effect for vocal stem FX slot
effect_select 'colorfx' 'filter'    # Select ColorFX
filter_selectcolorfx 'echo'         # Select ColorFX (alternative)
effect_mixfx_select 'echo'          # Select Mix FX

# ACTIVATION
effect_active 1                     # Toggle slot 1
effect_active 1 on                  # Turn on slot 1
effect_active 'echo'                # Shortcut: toggle Echo by name
effect_active 'vocals'              # Toggle vocal stem FX slot
effect_active 'colorfx'             # Toggle ColorFX
effect_mixfx_activate               # Toggle Mix FX

# PARAMETERS
effect_slider 1 1 50%               # Slot 1, param 1 = 50%
effect_slider 1 2 1bt               # Slot 1, param 2 = 1 beat
effect_slider 'vocals' 1 50%        # Vocal stem FX slot, param 1 = 50%
effect_slider 'echo' 1 75%          # Shortcut: Echo param 1 by name
filter 50%                          # ColorFX/filter = 50%

# BUTTONS
effect_button 1 1                   # Press button 1 on slot 1
effect_button 'echo' 2              # Press button 2 on Echo

# DYNAMIC CONTROLS
effect_has_slider 1 1               # Does slot 1 expose slider 1?
get_effect_slider_label 1 1         # Label for slot 1 slider 1
get_effect_slider_default 1 1 0.5   # Default/center hint
effect_has_button 1                 # Does selected effect expose button 1?
get_effect_button_shortname 1       # Compact button label

# GUI
effect_show_gui 1                   # Show GUI for slot 1
effect_show_gui 'colorfx'           # Show ColorFX GUI
effect_show_gui 'vocals' 'echo'     # Show stems FX GUI

# STEMS FX
effect_stems 'vocal'                # Apply to vocals
effect_stems 'melorhythm'           # Apply to instruments
effect_stems off                    # Disable stems FX
effect_select 'vocals' 'reverb'     # Load Reverb in the vocal stem FX slot

# PAD FX
padfx 'echo' 50% 1bt                # Trigger echo
padfx_single 'echo out' 80% 1bt     # One-shot echo out
padfx 'reverb' 75% 'stemfx:vocal'   # Reverb on vocals

# MASTER FX
deck master effect_select 1 'reverb'
deck master effect_active 1
deck master effect_slider 1 1 50%

# VIDEO FX
deck master video_fx_select 'spectral'
deck master video_fx
deck master video_fx_slider 1 50%
video_transition_select 'fade'
video_transition 1000ms

# ADVANCED FX HELPERS
effect_bank_save 1                  # Save deck FX slots 1-6 to bank 1
effect_bank_load 1                  # Load deck FX bank 1
effect_3slots_layout                # Toggle 1-slot / 3-slot layout
effect_releaseslider_active 50%     # Move release-FX slider and activate
effect_fxsendreturnenable           # Enable/query send-return path

# QUERIES
effect_active 1                     # Is slot 1 active?
effect_active 1 'echo out'          # Is Echo Out active in slot 1?
effect_stems                        # Is stems FX active?
get_effect_name 1                   # Get name of effect in slot 1
get_effect_slider_count             # Count sliders in the current FX context
get_effect_button_count             # Count buttons in the current FX context
filter_label                        # Get ColorFX name
effect_mixfx_select                 # Get selected Mix FX name
get_videofx_name                    # Get selected video FX name
is_releasefx                        # Is the release-FX slot/state active?

Common Effect Values

Strength/Dry-Wet:

0% = No effect
50% = Half mix
100% = Full effect

Beat Values:

0.25bt = 1/4 beat
0.5bt = 1/2 beat
1bt = 1 beat
2bt = 2 beats
4bt = 1 bar

Time Values:

100ms = 0.1 seconds
500ms = 0.5 seconds
1000ms = 1 second

Summary

VirtualDJ's effect system is powerful and flexible:

ColorFX - Quick one-knob filter/effects
Mix FX - Crossfader-linked transition effects
Deck FX Slots - Full multi-parameter effects (3-6 slots)
Master FX - Global effects on master output
Video FX - Visual effects and transitions
Stems FX - Effects on individual stems
Pad FX - Quick-trigger preset effects

Key Principles:

Effects can be controlled by slot number or by name
FX1-FX6 are persistent rack state; Pad FX and named stem FX slots are volatile performance state
Pre-fader is default and recommended for most use cases
Stems FX requires pre-fader processing
ColorFX is always pre-fader (integrated with EQ engine)
Mix FX is selected with effect_mixfx_select and toggled with effect_mixfx_activate; test direct selection queries before using them for skin state
Effects can be chained for creative combinations
Use variables to track complex effect states

Best Practices:

Organize effects into custom lists
Learn your most-used effects thoroughly
Use Stems FX for creative vocal/instrument manipulation
Combine Pad FX with variables for complex workflows
Check resetFXOnLoad option to avoid effect carryover
Test effects with different audio material

This guide covers the core effect engines in VirtualDJ. Experiment with combinations to develop your signature sound!

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Effects Engines.md

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Effects Engines.md

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Effects Engines

Overview

ColorFX (Filter Slot)

What is ColorFX?

Key Characteristics

ColorFX vs Regular Filter

Available ColorFX Effects

VDJScript Commands

Practical Usage

Important Notes

Mix FX (Crossfader-Linked FX)

What is Mix FX?

VDJScript Commands

Querying the Selected Mix FX

Source Status

Deck FX Slots (FX1, FX2, FX3, etc.)

What are Deck FX Slots?

Slot Configuration

VDJScript Commands

Checking if Effects are Active

Effect by Name (Convenience Shortcut)

Effect Chaining

Practical Usage Patterns

Master FX

What is Master FX?

Targeting Master Deck

Master FX Use Cases

Practical Example

Video FX

What are Video FX?

Video FX Categories

VDJScript Commands

Practical Usage

Stems FX

What is Stems FX?

How Stems FX Works

Stem Selection Options

VDJScript Commands

Stems FX from GUI

Stems FX Pad Page

Practical Usage

Limitations and Notes

Source Status

Pad FX

What is Pad FX?

Pad FX Characteristics

VDJScript Commands

Pad FX Parameter Order

Working Pad FX Parameter Examples

Checking Pad FX Status

Show Pad FX GUI

Practical Usage

Pre-Fader vs Post-Fader

What's the Difference?

Signal Flow

When to Use Each

Setting FX Processing Mode

Important Notes

Effect Queries and Conditionals

Checking Effect Status

Visual Feedback Examples

Effect Introspection and Dynamic Controls

Practical Effect Workflows

Workflow 1: Echo Out Transition

Workflow 2: Beatgrid Breakdown

Workflow 3: Vocal Echo with Stems

Workflow 4: Build Up with Multiple Effects

Workflow 5: Acapella Out with Reverb

Effect Lists and Organization

Creating Effect Lists

Managing Effect Lists

List Editor Functions

Practical List Examples

Advanced Effect Techniques