SF2Create

Create SoundFont v2 (.sf2) files from WAV data using JavaScript.

Note: this module was largely written by an LLM with some human feedback.

Install

npm install sf2create

Usage

Basic usage: const sf2Blob = createSf2File(dataStructure)

Example: Melodic Instrument

import { createSf2File } from './create-sf2.mjs';
import fs from 'fs';

// Define your sound data
const soundData = {
  name: 'MySoundFont',
  author: 'My Name', // Optional, defaults to the package name
  samples: [
    {
      name: 'piano',
      rawMonoData: new Float32Array(44100).fill(0.5), // 1 second of sound
      sampleRate: 44100,
      rootNote: 60,
    }
  ],
};

// Create the SoundFont file
const sf2Blob = createSf2File(soundData);

// Write to disk
fs.writeFileSync('output.sf2', Buffer.from(await sf2Blob.arrayBuffer()));

Example: Drum Kit

To create a drum kit, set isDrumKit: true. The rootNote for each sample specifies the MIDI key it maps to. If rootNote is not provided, it will be inferred from the sample name based on the General MIDI drum map.

import { createSf2File } from './create-sf2.mjs';
import fs from 'fs';

const drumData = {
  name: 'MyDrumKit',
  isDrumKit: true,
  samples: [
    {
      name: 'Kick', // Will default to rootNote 36
      rawMonoData: new Float32Array(22050).fill(0.9),
    },
    {
      name: 'Snare', // Will default to rootNote 38
      rawMonoData: new Float32Array(22050).fill(0.8),
    },
    {
      name: 'Open Hi-Hat', // Defaults to rootNote 46, exclusiveClass 1
      rawMonoData: new Float32Array(44100).fill(0.5),
    },
    {
      name: 'Closed Hi-Hat', // Defaults to rootNote 42, exclusiveClass 1
      rawMonoData: new Float32Array(11025).fill(0.6),
    }
  ]
};

const sf2Blob = createSf2File(drumData);
fs.writeFileSync('drumkit.sf2', Buffer.from(await sf2Blob.arrayBuffer()));

Command-Line Tool

A basic command-line tool create-sf2-from-wavs.mjs is included for converting .wav files into an SF2 instrument.

For melodic instruments, filenames must contain a note name (e.g., MySample-A4.wav).

node create-sf2-from-wavs.mjs "MyInstrument" samples/*.wav

For drum kits, use the --drums flag. Note names are not required; the tool will use sample names (e.g., kick.wav, snare.wav) to look up default MIDI notes.

node create-sf2-from-wavs.mjs --drums "MyDrumKit" drum-samples/*.wav

Testing

Run the tests:

npm test

Notes

• Supports 16-bit mono and stereo samples.
• Loop points can be specified for samples.
• Supports basic melodic instruments and GM-compatible drum kits.

Technical references

• https://www.synthfont.com/SFSPEC21.PDF
• https://github.com/FluidSynth/fluidsynth