Yamaha introduced Music Cartridges in 1995 for use in some of its PSR range of entry-level and mid-range keyboards. These are not to be confused with an earlier Music Cartridge format from Yamaha that was used on its TYU-30 model in 1986.
The Yamaha Music Cartridge for PSR models were ROM cartridges containing either fully-arranged songs, or additional styles to add to the keyboard’s library, and were inserted into a slot on top of the keyboard. Six models of keyboard were able to accept Music Cartridges – PSR-320, PSR-420, PSR-520 and PSR-620, launched in 1995, and the PSR-330 and PSR-530, launched in 1997.
Later models of Yamaha keyboard used 3.5-inch floppy disks.