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

Apart from breaking changes to the Dart language (rare), since this package has no dependencies it should work on any Dart SDK >=2.12 indefinitely. This package was written against Dart SDK 2.16.1.

Example

Ssynthesize 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);

Features

• No memory allocation in the rendering process.

• Wave synthesis

  • SoundFont reader
  • Waveform generator
  • Envelope generator
  • Low-pass filter
  • Vibrato LFO
  • Modulation LFO

• MIDI message processing

  • Note on/off
  • Bank selection
  • Modulation
  • Volume control
  • Pan
  • Expression
  • Hold pedal
  • Program change
  • Pitch bend
  • Tuning

• Effects

  • Reverb
  • Chorus

• Other things

  • Loop extension support
  • Performace optimization

• MIDI file support.

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

// Read the MIDI file.
var midiFile = MidiFile.fromFile("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