Musicard

The Musicard is a music format developed by Theorysonic, and  in 1997 and released in January 1998 by the three manufacturers. 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 and Videocard MobilePlayer or through a driver hooked up to a computer or TV with TheoryMedia, Musicard Viewer, or other media players (some require extensions). Musicards only support MP3 format when writing to them.

Theorysonic invested heavily into the development and release of the Musicard, which included getting labels to issue Musicard-exclusive titles; along with Theorysonic, Sony and SanDisk jointly building a factory in solely for Musicard production. As of 2019, the Musicard continues to be manufactured and sold, albeit to a niche market.

The highest-selling Musicard was ' , which sold over 17 billion copies worldwide