midi2audio

Easily synthesize MIDI to audio or just play it.

It provides a Python and command-line interface to the FluidSynth synthesizer to make it easy to use and suitable for scripting and batch processing. In contrast, most MIDI processing software is GUI-based.

Why?

First, FluidSynth has a CLI which is not so straightforward to use. The goal was to make it easy to use as possible by making some parameters implicit.

fluidsynth -ni sound_font.sf2 input.mid -F output.wav -r 44100

vs.

midiplay input.mid
midi2audio input.mid output.wav

Second, we can have as easy interface scriptable in Python.

FluidSynth().midi_to_audio('input.mid', 'output.wav')

What it is not?

Note that is it not a Python binding to all the FluidSynth commands. If needed check out these packages instead:

• fluidsynth
• pyFluidSynth

Requirements

• Python 3
• FluidSynth
• some sound font(s)

You need at least one sound font. Normally you'd install them manually or via a package manager. midi2audio looks for its default sound font in ~/.fluidsynth/default_sound_font.sf2. It can be a symlink or an actual file.

Installation

pip

You can install this package via pip.

pip install midi2audio

Or for development (changes in code take effect without reinstalling):

git clone https://github.com/bzamecnik/midi2audio
pip install -e midi2audio

OS X

I'd recommend adding the non-default libsndfile which supports output to FLAC and wide variety of audio formats. Otherwise only WAV, raw and a few other will be supported.

For Mac OS X we provide a script install_fluidsynth_with_soundfonts_osx.sh to automatically install FluidSynth with libsndfile and a basic sound font (Fluid R3 GM) and symlink it so that it's recognized as a default sound font for this module. Note it it install installed via pip as another entry point.

install_fluidsynth_with_soundfonts_osx.sh

Or install it manually:

brew install fluidsynth --with-libsndfile
mkdir -p ~/.fluidsynth
ln -s /path/to/my/sound_font.sf2 ~/.fluidsynth/default_sound_font.sf2

Check the script how to install a few additional (nice but bigger) sound fonts which are not installed by default.

Other OSs

Check you package manager and link your default sound font as descibed above.

Usage

Basically you can either play a MIDI file or synthesize it to audio. FluidSynth allows non-realtime synthesis which is faster than the playback.

Note that the audio format is determined from the audio file extension. The libsoundfile supports a lot of formats.

Python

from midi2audio import FluidSynth

Play MIDI:

FluidSynth().play_midi('input.mid')

Synthesize MIDI to audio:

# using the default sound font in 44100 Hz sample rate
fs = FluidSynth()
fs.midi_to_audio('input.mid', 'output.wav')

# optional third argument to control gain (defaults to 0.2)
fs.midi_to_audio('input.mid', 'output.wav', gain=0.75)

# FLAC, a lossless codec, is supported as well (and recommended to be used)
fs.midi_to_audio('input.mid', 'output.flac')

Change the defaults:

# use a custom sound font
FluidSynth('sound_font.sf2')

# use a custom sample rate
FluidSynth(sample_rate=22050)

Command line interface

A shell sugars midi2audio and midiplay are provided instead of more verbose python -m midi2audio.

# play MIDI
$ midiplay input.mid

# synthesize MIDI to audio
$ midi2audio input.mid output.wav

# also to FLAC
$ midi2audio input.mid output.flac

# custom sound font
$ midi2audio -s sound_font.sf2 input.mid output.flac

# custom sample rate
$ midi2audio -r 22050 input.mid output.flac

About

• Author: Bohumír Zámečník (@bzamecnik)
• License: MIT, see the LICENSE file

Shoulders of giants

Thanks to the authors of FluidSynth for a nice command-line MIDI synthesizer!

Support the project

Need some consulting or coding work regarding audio processing, machine learning or big data? Drop me a message via email or LinkedIn. Or just say hello :).