midi-synth
Skill21 starsChanged 7 months agoMITView on GitHub
Synthesize and render MIDI/MusicXML files to audio (WAV/MP3) and generate Strudel live-coding patterns for creative music manipulation. Uses analysis data (tempo, key, chords, dynamics) from audio-to-midi for intelligent ghost-note removal and accurate reproduction. Two workflows: (1) Convert MIDI/MusicXML to Strudel/TidalCycles code with note durations for interactive tweaking in the browser at strudel.cc, (2) Render MIDI/MusicXML to WAV/MP3 with FluidSynth or built-in synthesis, with controls for tempo, transposition, instrument override, and ghost-note cleaning. Trigger when the user wants to: play a MIDI file, render MIDI to audio, synthesize MIDI, convert MIDI to Strudel code, create live-coding patterns from MIDI, change instruments, transpose or tempo-shift, clean ghost notes, or any MIDI playback/synthesis task.
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The file
We split this skill into the rules it gives an agent
2 rules. About 0 are common, 2 are distinctive, and 0 are very specific to this project.
≈0
Common · estimate
Many files like this have a rule of this kind.
≈2
Distinctive · estimate
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0
Very specific
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- Common
- Distinctive
- Very specific
- Distinctive: line 35
Both: run both on the same input
- Distinctive: line 110
Key filter: if analysis provides a key, removes out-of-key notes that also have low velocity (<60)
≈ “Common” is an estimate: at least 1 in 5 of the 350,495 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.
Files
MIDI Synth
Synthesize MIDI/MusicXML to audio and generate Strudel live-coding patterns. Uses analysis data for ghost-note cleaning, correct tempo, and key-aware filtering.
Scripts
scripts/to_strudel.py-- MIDI/MusicXML to Strudel patterns with duration-aware notationscripts/render.py-- MIDI/MusicXML to WAV/MP3 with cleaning and modifications
Both scripts auto-detect *_analysis.json files from audio-to-midi for tempo, key, and dynamics.
Workflow
- Identify input: MIDI (.mid) or MusicXML (.musicxml)
- Auto-detect or specify the analysis JSON from audio-to-midi
- Choose workflow:
- Creative:
to_strudel.pygenerates Strudel code for strudel.cc - Rendering:
render.pyproduces WAV/MP3 - Both: run both on the same input
- Creative:
- Ghost notes are automatically cleaned using velocity, duration, and key filters
Strudel Code Generation
# Basic (auto-detects analysis JSON next to input)
py -3.12 scripts/to_strudel.py "song.mid"
# From MusicXML
py -3.12 scripts/to_strudel.py "song.musicxml"
# Explicit analysis file
py -3.12 scripts/to_strudel.py "song.mid" --analysis "song_analysis.json"
# Stricter ghost-note filtering
py -3.12 scripts/to_strudel.py "song.mid" --min-velocity 60 --min-duration 0.1
# Open in browser
py -3.12 scripts/to_strudel.py "song.mid" --open| Flag | Default | Effect |
--analysis | auto-detect | Path to analysis JSON for tempo/key |
--bars | 4 | Pattern length in bars |
--resolution | 16 | Grid: 4/8/16/32 |
--min-velocity | 40 | Remove notes below this velocity (0-127) |
--min-duration | 0.05 | Remove notes shorter than this (seconds) |
--no-key-filter | off | Disable key-based ghost note filtering |
--tempo | from analysis | Override tempo BPM |
--open | off | Open in strudel.cc in browser |
Note durations are encoded with @N notation (e.g., c3@4 = held for 4 steps).
Audio Rendering
# Basic (auto-detects analysis, cleans ghost notes)
py -3.12 scripts/render.py "song.mid" --mp3
# From MusicXML
py -3.12 scripts/render.py "song.musicxml" --mp3
# With SoundFont
py -3.12 scripts/render.py "song.mid" --soundfont "GeneralUser_GS.sf2" --mp3
# Aggressive cleaning
py -3.12 scripts/render.py "song.mid" --min-velocity 60 --min-duration 0.1
# Skip cleaning entirely
py -3.12 scripts/render.py "song.mid" --no-clean
# Modifications
py -3.12 scripts/render.py "song.mid" --tempo 2.0 --transpose 3 --instrument 0| Flag | Default | Effect |
--analysis | auto-detect | Analysis JSON for tempo/key-based cleaning |
--min-velocity | 40 | Ghost note velocity threshold |
--min-duration | 0.05 | Ghost note duration threshold (seconds) |
--no-clean | off | Skip ghost note removal |
--no-key-filter | off | Disable key-based filtering |
--soundfont | auto-detect | .sf2 SoundFont path |
--tempo | 1.0 | Tempo scale factor |
--transpose | 0 | Semitones up/down |
--instrument | original | Override GM program (0-127) |
--mp3 | off | Also produce MP3 |
Ghost Note Cleaning
Three filter layers (applied in order):
- Velocity filter: removes notes below
--min-velocity(default: 40) - Duration filter: removes notes shorter than
--min-duration(default: 50ms) - Key filter: if analysis provides a key, removes out-of-key notes that also have low velocity (<60)
The key filter only removes notes that are BOTH out-of-key AND below medium velocity, preserving intentional chromatic passages.
Dependencies
Auto-installed: pretty_midi, numpy, soundfile.
For MusicXML input: music21 (installed by audio-to-midi skill).
Optional: pyfluidsynth + .sf2 SoundFont for high-quality rendering.
Runtime: Python 3.12 (py -3.12).
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