frodo

Music JSON -> MIDI (Standard MIDI File) compiler in Rust. The goal is to let LLMs describe music at a musical level (beats, patterns, instruments) and hide MIDI delta-time details.

Build

cargo build

CLI

Create a starter song JSON:

cargo run -- new --out song.json

Compile JSON -> MIDI:

cargo run -- json2midi --input song.json --output out.mid

Listen:

timidity out.mid

Library

Primary API is in src/song.rs and exported via src/lib.rs:

• compile_song_json(json: &str) -> Result<Smf, SongCompileError>
• Smf::to_bytes() -> Vec<u8>

Examples

• examples/techno_v2.json
• examples/neon_relay_v2.json
• examples/rock_tv_jingle_raw.json
• examples/song_v1.json

JSON Notes (v2)

v2 supports clips, step-sequencer lanes, per-lane groove, and CC/pitch-bend automation (points + ramps).

The v2 loader normalizes some common LLM outputs:

• time_signature may be "4/4" (string) or an object.
• steps.lanes may be an array (preferred) or an object map ({\"kick\": {...}}).
• Notes may use start_beat/duration_beats (aliases for start/duration).
• Chords may use pitches: [...] (expanded into multiple notes).