In case this is the first you've heard of "100% scheduled" and "web audio native":

By "100% scheduled" we mean that all the timing of audio events is handled using the web audio scheduler. Jerrica doesn't use setTimeout, setInterval, or other timing hacks. It is recommended that its processMusic function is called once per frame via requestAnimationFrame, but that's simply to ensure that sound events are always scheduled well ahead of when they need to occur.

By "web audio native" we mean that all audio effects are achieved via the web audio API. Many audio players manipulate audio at the sample level, treating web audio as a "dumb pipe" for an audio buffer. Jerrica doesn't do that. After loading the samples from the MOD file, Jerrica only ever uses web audio functions to manipulate the sounds, for example via the playbackRate AudioParam.

To the author's credit, these are both explained near the top of the README. Cheers.