In a week that will see heavy coverage of MySpace Music when it launches, SanDisk (NSDQ: SNDK) has announced an ambitious venture to sell its microSD memory cards pre-loaded with DRM-free MP3 music from all the four majors EMI Music, Sony BMG, Universal Music Group, and Warner Music Group. The service, dubbed “slotMusic”, will launch this coming holiday season in U.S., at Best Buy and Wal-Mart (NYSE: WMT), among others, and then will be launched in Europe, though no specific timeline was given. The MicroSD format, a SanDisk invention, is used mainly in mobile phones, and also in some MP3 players. When slotMusic goes on dale, these cards will be packaged with a tiny USB sleeve so that they can be compatible with various PCs and laptops, and any other device with a USB connector, including say an in-car sound system. The MP3-based music tracks will be played back at up to 320 kbps, the company said. With 1GB of capacity, slotMusic cards can hold songs, as well as liner notes, album art, videos, and other content that an artist/labels may choose.