Module file formats [0] have been around since the 80s, and they can kind of be thought of as MIDI files with sound samples embedded in them. You can get some very impressive sounding full-length tracks in only a few kilobytes.
Are you asking for library recommendations for a simple standard used extensively for the last 35 years when there are already 6 libraries linked in the wikipedia page you were given?
MIDI (1.0) is more equivalent to NES/GameBoy-style sprites. It was designed almost exclusively with piano-like keyboard controllers in mind, suffers from a lot of 80's-era hardware limitations, heavily biased towards western music, relies completely on the sound bank for actual rendering (you can't even set your own pixels on a sprite - you can only say "paint a Mario here"), relies in some places on vendor-specific extensions, overall really it hasn't aged as nicely as say TCP.
A true "SVG, but for music" kind of equivalent would be an insanely interesting and challenging project. I'm not even sure if it should strive for more of a middle ground (so it can gain widespread adoption), or for flexibility (so it doesn't constrain creativity and allows expressiveness).
