DartMeltySoundFont

DartMeltySoundFont is a SoundFont synthesizer (i.e. '.sf2' player) written in pure Dart.

It is a port of MeltySynth (C#, MIT License) written by Nobuaki Tanaka, to Dart.

https://github.com/sinshu/meltysynth

Dependencies

This package has no dependencies.

Maintanence

This project was specifically designed to not require maintanence, in large part by not having any dependencies. Apart from breaking changes to the Dart language (rare), it should be solid code that works for decades. It will work on any Dart SDK sdk>=2.12 && sdk<3.0 indefinitely.

This package was written against Dart SDK 2.16.1.

Example

Synthesize a simple chord:

// Necessary Imports
import 'package:dart_melty_soundfont/dart_melty_soundfont.dart';
import 'package:flutter/services.dart' show rootBundle;

// Create the synthesizer.
ByteData bytes = await rootBundle.load('assets/akai_steinway.sf2');

Synthesizer synth = Synthesizer.loadByteData(bytes, 
    SynthesizerSettings(
        sampleRate: 44100, 
        blockSize: 64, 
        maximumPolyphony: 64, 
        enableReverbAndChorus: true,
    ));

// you might want to select the patchNumber & bankNumber
// of the instrument you want to play, if it's not 0.
//
// Look through synth.soundFont.presets[X].patchNumber & bankNumber
// for all valid instrument choices.
//
// Example for setting patchNumer:
//
// int patchNumber = synth.soundFont.presets[0].patchNumber 
// synth.processMidiMessage(
//  channel:0, 
//  command:0xC0, // 0xC0 = program changes
//  data1:patchNumber, 
//  data2:0
// );
//
// Example for setting bankNumber:
//
// int bankNumber = synth.soundFont.presets[0].bankNumber 
// synth.processMidiMessage(
//  channel:0, 
//  command:0xB0, // 0xB0 = control change
//  data1:0x00,   // 0x00 = bank select
//  data2:bankNumber,
// );


// Turn on some notes
synth.noteOn(channel: 0, key: 72, velocity: 120);
synth.noteOn(channel: 0, key: 76, velocity: 120);
synth.noteOn(channel: 0, key: 79, velocity: 120);
synth.noteOn(channel: 0, key: 82, velocity: 120);


// Render the waveform (3 seconds)
ArrayInt16 buf16 = ArrayInt16.zeros(numShorts: 44100 * 3);

synth.renderMonoInt16(buf16);

Playing Sound

This library does not audibly make sound, it only generates the PCM waveform.

To actually hear something, you need to pass the generated PCM waveform to your device's speakers. I recommend using raw_sound or Web Audio for that task, depending on your platform.

See raw_sound's PCM audio example, for iOS and Android.

Features

• No memory allocation in the rendering process.

• 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

  • x Reverb
  • x Chorus

• Other things

  • x Loop extension support
  • x Performace optimization

Todo

• MIDI file support.

Feel free to port MIDI file support to Dart and make a pull request.

Its usage would look like this when implemented:

// Create the synthesizer.
var sampleRate = 44100;
var synthesizer = new Synthesizer("TimGM6mb.sf2", sampleRate);

// Read the MIDI file.
var midiFile = MidiFile("flourish.mid");
var sequencer = MidiFileSequencer(synthesizer);
sequencer.play(midiFile, false);

// Render the waveform (3 seconds)
ArrayInt16 buf16 = ArrayInt16.zeros(numShorts: 44100 * 3);

sequencer.renderMonoInt16(buf16);

License

DartMeltySoundFont is available under the MIT license.

References

• SoundFont® Technical Specification
  http://www.synthfont.com/SFSPEC21.PDF

• Polyphone Soundfont Editor
  Some of the test cases were generated with Polyphone.
  https://www.polyphone-soundfonts.com/

• Freeverb by Jezar at Dreampoint
  The implementation of the reverb effect is based on Freeverb.
  https://music.columbia.edu/pipermail/music-dsp/2001-October/045433.html