I looked into it and it seems like the only current technologies that could do this is m-disk or eeprom. M-disk doesn't fit my cartridge concept but is theoretically stable for up to 1000 years. Eeprom is not commercially made bigger than 4MB so is out for anything larger than a couple songs, but is allegedly also very stable.
I saw something about 5D data crystals but it seems like something that's pretty far off (if ever) for the consumer market