What does it even mean for a piece of music to be so long that no person could possibly listen to it? And supposedly you can download the entire piece and it’s only a few hundred kilobytes in size? Shouldn’t it take more atoms than exist in the universe to store a piece of music so large? Or is compression that effective?
EDIT: eg https://bullofheavendc.bandcamp.com/album/310-px0-2-18-5-18-p-k-k-k
I don’t know about repeating or being able to have very long playtimes, but I do know the MIDI (.mid) file format can play songs at extremely small sizes compared to mp3 as it effectively stores the sound like music on a sheet which is played by a synthesizer. Also the MOD file format allows samples to be recorded as a sort of blend of synth and recordings.