Py-MeltySynth

Py-MeltySynth is a SoundFont MIDI synthesizer written in pure Python, ported from MeltySynth for C#. I believe this is the first fully functional SoundFont synthesizer made with Python without external libraries.

Features

• Support for standard MIDI files.
• No dependencies other than the standard library.
• All the functionality is in a single file. Simply copy the file into your project and you are ready to go.

Demo

https://www.youtube.com/watch?v=Pheb0pSzQP8

Development status

It works, but it's slow. Without external libraries, sample-by-sample audio processing seems tough for Python... But Python is said to be becoming more performance oriented, so it should be useful in the future.

Below is a comparison of the time it took to render a MIDI file in several languages. The MIDI file is flourish.mid (90 seconds) and the SoundFont used is TimGM6mb.sf2. Python is still slow, but it is certainly improving in speed as the versions go up.

Examples

An example code to synthesize a simple chord:

import meltysynth as ms

# Load the SoundFont.
sound_font = ms.SoundFont.from_file("TimGM6mb.sf2")

# Create the synthesizer.
settings = ms.SynthesizerSettings(44100)
synthesizer = ms.Synthesizer(sound_font, settings)

# Play some notes (middle C, E, G).
synthesizer.note_on(0, 60, 100)
synthesizer.note_on(0, 64, 100)
synthesizer.note_on(0, 67, 100)

# The output buffer (3 seconds).
left = ms.create_buffer(3 * settings.sample_rate)
right = ms.create_buffer(3 * settings.sample_rate)

# Render the waveform.
synthesizer.render(left, right)

Another example code to synthesize a MIDI file. It will take a long time 😉

import meltysynth as ms

# Load the SoundFont.
sound_font = ms.SoundFont.from_file("TimGM6mb.sf2")

# Create the synthesizer.
settings = ms.SynthesizerSettings(44100)
synthesizer = ms.Synthesizer(sound_font, settings)

# Load the MIDI file.
midi_file = ms.MidiFile.from_file("flourish.mid")

# Create the MIDI sequencer.
sequencer = ms.MidiFileSequencer(synthesizer)
sequencer.play(midi_file, False)

# The output buffer.
left = ms.create_buffer(int(settings.sample_rate * midi_file.length))
right = ms.create_buffer(int(settings.sample_rate * midi_file.length))

# Render the waveform.
sequencer.render(left, right)

Todo

• Wave synthesis
  • [x] SoundFont reader
  • [x] Waveform generator
  • [x] Envelope generator
  • [x] Low-pass filter
  • [x] Vibrato LFO
  • [x] Modulation LFO
• MIDI message processing
  • [x] Note on/off
  • [x] Bank selection
  • [x] Modulation
  • [x] Volume control
  • [x] Pan
  • [x] Expression
  • [x] Hold pedal
  • [x] Program change
  • [x] Pitch bend
  • [x] Tuning
• Effects
  • [ ] Reverb
  • [ ] Chorus
• Other things
  • [x] Standard MIDI file support
  • [ ] Loop extension support
  • [ ] Performace optimization

License

Py-MeltySynth is available under the MIT license.