Musicard

The Musicard is a music format invented by Theorysonic in 1997 and released in 1998. The format is a standard flash card format, measuring 3.5 by 3.5 cm in diameter. The cards can only be read on dedicated players such as the Portosic MC, or through a driver hooked up to a computer or TV with TheoryMedia, Musicard Viewer, or other media players (some requires extensions). Musicards only support MP3 format when writing to them.

The Musicard was exported and marketed in Japan as the Sony Musicard by Sony in 1999 and in the US as the Theory Musicard by SanDisk in 2000. As of 2019, the Musicard continues to be manufactured and sold, albeit to a niche market.

The biggest-selling Musicard was 's , which sold over 17 million copies.