Drone mode for the Pad (pedal point + cadence retriggers)

[philoking]

Summary

Extend the Pad into a proper drone / pedal-point voice. Today the Pad is one sustained, voice-led chord tone that moves with each chord (padMode: 'note', with a 'chord' option already in state). Add a mode that holds a fixed root/pedal regardless of chord changes, plus an option to retrigger the pad on a chosen cadence instead of only re-sounding on chord changes.

Why it fits

The held drone and the moving pedal point are core ambient/modular textures, and the Pad is the natural home for them. A pedal tone under shifting harmony is one of the easiest ways to make a long Modular Riffs jam feel intentional and cinematic.

Proposed scope

Pad behaviour (js/generator.js)

• Add to the existing padMode: pedal (or root) — the Pad locks to the key's tonic (or a chosen scale degree) and ignores chord changes, becoming a drone under the moving parts.
• Retrigger cadence: instead of only sounding on chord change, optionally re-strike on a selectable pattern — e.g. on 1, on 1 & 3, on every beat, or off (pure sustain). Reuse the existing gate-length control for how long each strike holds.
• Keep voice-leading behaviour intact for the existing 'note' mode.

UI (js/app.js)

• Pad ⚙ gains a mode select (note / chord / pedal) and, when retrigger is on, a cadence picker.
• Optional pedal degree chooser (default tonic) so the drone can sit on the 5th, etc.

Where

js/generator.js (pad generation, retrigger timing), js/app.js (Pad ⚙ controls + state).

Done when

• Pad can hold a fixed pedal/root that ignores chord changes.
• Pad can retrigger on a selectable cadence, or sustain.
• Existing note / chord modes unchanged.
• Settings persist in presets / JSON.

Open questions

• The pedal degree should follow key changes automatically — confirm how it interacts with per-section transposition.
• Retrigger timing under per-part clock divide — define which clock the cadence counts in.