Soundfonts for web. About of 2000 musical instruments. GM MIDI compatible.

webaudiofont

midi-sounds-react

A set of functions for manipulating musical pitches within a given EDO

A web audio tuning library of microtonal and just intonation scales 

Convert Scala (.scl) tunings to MIDI note frequencies.

A harmony-based music composition toolkit with MIDI I/O

A microtonal-aware synth engine library for web.

Basic xen number types for microtonal scale representation and manipulation with TypeScript / JavaScript.