MIDI Chat Sequencer

A step sequencer driven by a chat-style CLI, designed to output MIDI to DAWs like Reason, Ableton, Logic, etc.

Install

uv sync

Windows only: Install loopMIDI and create a virtual port named Chat Sequencer.

Run

Web UI (recommended)

export ANTHROPIC_API_KEY=sk-ant-...  # optional, for AI natural language input
uv run uvicorn server:app --reload

Open http://127.0.0.1:8000. The web UI provides a pattern grid visualizer with dual input:

• Direct commands (left input) — same commands as the CLI
• AI input (right input) — describe what you want in plain English (requires ANTHROPIC_API_KEY)

CLI only

uv run python sequencer.py

Then in Reason (or any DAW), set a MIDI input to "Chat Sequencer".

Quick Example Session

♪ bpm 128
♪ new drums 16 9
♪ put drums 0,4,8,12 kick
♪ put drums 2,6,10,14 snare
♪ put drums 0-15 hihat 60
♪ new bass 16 0
♪ put bass 0,8 C2
♪ put bass 4 D#2
♪ put bass 12 G1
♪ play
♪ show drums
♪ euclid bass 5 C2,D#2,G1
♪ mute drums
♪ stop

Architecture

The ChatInterface.handle(line) method is the command dispatcher shared by both CLI and web UI. It returns (continue_flag, output_lines) so callers can capture output.

The web UI (server.py) uses FastAPI with WebSockets to push real-time state to the browser:

• Pattern grid visualization with live playhead
• Transport state (playing/stopped, BPM)
• Command output

The AI input uses Claude API to translate natural language into sequencer commands, then executes each via handle().

Key Concepts

• Patterns have a name, step count, and MIDI channel
• Steps are 16th notes by default (4 per beat)
• Euclidean rhythms distribute N hits evenly across the step grid
• Arp fills a pattern by cycling through notes in a given order
• Channel 9 = GM drums (use for Reason's drum machines)