A powerful soundfont/MIDI JavaScript library for the browsers.

npm install --save spessasynth_lib

import { Synthetizer } from "spessasynth_lib"

const sfont = await (await fetch("soundfont.sf3")).arrayBuffer();
const ctx = new AudioContext();
// make sure you copied the worklet processor!
await ctx.audioWorklet.addModule("./worklet_processor.min.js");
const synth = new Synthetizer(ctx.destination, sfont);
document.getElementById("button").onclick = async () =>
{
    await ctx.resume();
    synth.programChange(0, 48); // strings ensemble
    synth.noteOn(0, 52, 127);
}

• Modular design: Easy integration into other projects (load what you need)
• Detailed documentation: With examples!
• Easy to Use: basic setup is just two lines of code!
• No dependencies: batteries included!

• Suitable for both real-time and offline synthesis
• Excellent SoundFont support:
  • Full Generator Support
  • Full Modulator Support: First (to my knowledge) JavaScript SoundFont synth with that feature!
  • GeneralUserGS Certified: See more here!
  • SoundFont3 Support: Play compressed SoundFonts!
  • Experimental SF2Pack Support: Play soundfonts compressed with BASSMIDI! (Note: only works with vorbis compression)
  • Can load very large SoundFonts: up to 4GB! Note: Only Firefox handles this well; Chromium has a hard-coded memory limit
• Soundfont manager: Stack multiple soundfonts!
• DLS Level 1 and 2 Support: works with gm.dls!
• Reverb and chorus support: customizable!
• Export audio files using OfflineAudioContext
• Custom modulators for additional controllers: Why not?
• Written using AudioWorklets:
  • Runs in a separate thread for maximum performance
  • Supported by all modern browsers
• Unlimited channel count: Your CPU is the limit!
• Excellent MIDI Standards Support:
  • MIDI Controller Support: Default supported controllers here
  • MIDI Tuning Standard Support: more info here
  • Full RPN and limited NRPN support
  • Supports some Roland GS and Yamaha XG system exclusives
• High-performance mode: Play Rush E! note: may kill your browser ;)

• Supports MIDI formats 0, 1, and 2: note: format 2 support is experimental as it's very, very rare
• Multi-Port MIDI support: More than 16 channels!
• Smart preloading: Only preloads the samples used in the MIDI file for smooth playback (down to key and velocity!)
• Lyrics support: Add karaoke to your program!
• Raw lyrics available: Decode in any encoding! (Kanji? No problem!)
• Runs in Audio Thread as well: Never blocks the main thread
• Loop points support: Ensures seamless loops

• Smart name detection: Handles incorrectly formatted and non-standard track names
• Raw name available: Decode in any encoding! (Kanji? No problem!)
• Port detection during load time: Manage ports and channels easily!
• Used channels on track: Quickly determine which channels are used
• Key range detection: Detect the key range of the MIDI
• Easy MIDI editing: Use helper functions to modify the song to your needs!
• Loop detection: Automatically detects loops in MIDIs (e.g., from Touhou Project)
• First note detection: Skip unnecessary silence at the start by jumping to the first note!
• Write MIDI files from scratch
• Easy saving: Save with just one function!

• Level 4 compliance: Reads and writes everything!
• Compression and trimming support: Reduce a MIDI file with a 1GB soundfont to as small as 5MB!
• DLS Version support: The original legacy format with bank offset detection!
• Automatic bank shifting and validation: Every soundfont just works!
• Metadata support: Add title, artist, album name and cover and more! And of course read them too! (In any encoding!)
• Compatible with Falcosoft Midi Player 6!
• Easy saving: As simple as saving a MIDI file!

• Easy info access: Just an object of strings!
• Smart trimming: Trim the SoundFont to only include samples used in the MIDI (down to key and velocity!)
• sf3 conversion: Compress SoundFont2 files to SoundFont3 with variable quality!
• Easy saving: Also just one function!

• Same features as SoundFont2 but with now with Ogg Vorbis compression!
• Variable compression quality: You choose between file size and quality!
• Compression preserving: Avoid decompressing and recompressing uncompressed samples for minimal quality loss!

• Read DLS (DownLoadable Sounds) files as SF2 files!
• Works like a normal soundfont: Saving it as sf2 is still just one function!
• Converts articulators to both modulators and generators!
• Works with both unsigned 8-bit samples and signed 16-bit samples!
• Covers special generator cases: such as modLfoToPitch!
• Correct volume: looking at you, Viena and gm.sf2!
• Support built right into the synthesizer!
• Convert SF2 to DLS: with limitations;

• Save the MIDI file as WAV audio!
• Metadata support: Embed metadata such as title, artist, album and more!
• Cue points: Write MIDI loop points as cue points!
• Loop multiple times: Render two (or more) loops into the file for seamless transitions!
• That's right, saving as WAV is also just one function!

MIT License, except for the stbvorbis_sync.js in the externals folder which is licensed under the Apache-2.0 license.