

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.
My former coworkers (except I don’t know it cause … Someone used the flashy thing…)