midi-synth

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 notation
• scripts/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

1. Identify input: MIDI (.mid) or MusicXML (.musicxml)
2. Auto-detect or specify the analysis JSON from audio-to-midi
3. Choose workflow:
   • Creative: to_strudel.py generates Strudel code for strudel.cc
   • Rendering: render.py produces WAV/MP3
   • Both: run both on the same input
4. 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):

1. Velocity filter: removes notes below --min-velocity (default: 40)
2. Duration filter: removes notes shorter than --min-duration (default: 50ms)
3. 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).