Wikipedia
slotMusic was a brand of microSD memory card developed by SanDisk preloaded with music in MP3 format. They were first available at Wal-Mart and Best Buy stores in October 2008. The current selection of songs comes from Universal Music Group, Sony BMG, Warner Music Group and EMI Music. As of mid-2011, SanDisk's website lists a total of 14 albums available in the SlotMusic format.
The audio files contain no digital rights management, and are encoded at minimum bitrates of 256 to 320 kbit/s.
SlotMusic albums may also include high-quality images and videos in multiple formats. The contents of each microSD card may be altered by the user, enabling them to add or remove files from the slotMusic card as desired. Another type of card, slotRadio, has been developed for 2009 and has radiolike controls. SlotRadio has more restrictions on how it works, such as not being able to backtrack to a previous song.