Another visitor to the site can discover and then playback this drum track from their browser while jamming along, for example, with a guitar. (The web client would of course have to be capable of playing back audio while also capturing audio in real time.)
The visitor can also mix to a limited degree this two-track piece — panning, adjusting faders, perhaps some simple effects like compression, reverb. They can upload their guitar accompaniment along with pan/fader/effects settings to create a new mix.
Third visitor can pull down the composition and can contribute, for example, a bass line. Mix and upload and ... you get the point.
Perhaps a reasonable cap at 8 tracks so the client is not strained mixing/playing-back (never mind download overhead as the track count grows).
In a kind of free for all (that may remind some of you of git) anyone is free to replace tracks, go back to early mixes, etc. There's no fighting to speak of since every edit becomes its own "branch".
(A rating system ought to help separate the wheat from the chaff.)
If something like this exists, let me know. If it doesn't, I'll have to learn how to code it.
Sorry about the long answer, most of it is just context in case someone else less accustomed with music finds this thread interesting (oh, also Audio Worklets are really cool but that would warrant another 3 paragraphs hahaha) :). Despite the amount of similar neat options available, hope you decide to make it anyway! It has potential and would recommend it to people for sure.