Pre-loaded with MP3 tunes from the "big four" labels, SanDisk's DRM-free, microSD-based, USB-enabled slotMusic cards will be sold during the upcoming holiday season in Best Buys and Wal-Marts.

SanDisk today anounced "slotMusic" -- a new service to sell memory cards pre-loaded with DRM-free music from major record labels -- just three years after trying to launch a similar service dubbed "gruvi." Revolving around microSD, a flash memory format created by SanDisk, slotMusic will be supported by "big four" record labels EMI, Sony BMG (soon to become SMEI), Warner, and Universal.

During the upcoming holiday season, Best Buy, Wal-Mart, and other US retailers will begin to sell microSD memory cards pre-loaded with MP3 music in their brick-and-mortar stores. In a statement, SanDisk said that the service will subsequently be launched in Europe. Users will be able to play back MP3 music tracks from the cards at up to 320 Kbps.

The MicroSD format is used mostly in smartphones but also in some MP3 players, including many of SanDisk's own Sansa models. SanDisk plans to package the slotMusic microSD cards in small USB sleeves for playback on laptops, desktop PCs, in-car audio systems, and other devices outfitted with USB connectors.

BetaNews notes that many laptops also contain SD slots which are capable of using content formatted in microSD. Apple's briskly selling iPhone, however, does not contain either microSD or SD slots. It has a standard iPod connector which connects to USB on the opposite end, but it has no mini-USB.

The 1 GB slotMusic cards are capable of holding songs, videos, album art, liner notes, and other content chosen by artists or record labels, according to officials. Also, users will be able to download other content onto the cards.

Either the stars are coming into alignment on their own, or someone is helping to put them there. SanDisk is already a major provider of Sansa MP3 players to Best Buy stores; and up until very recently, Sansa players with RealNetworks' Rhapsody was supported by Best Buy's online music store. Last week, Best Buy acquired the Napster brand for what some would say was...well, a song. So now, a new distribution medium, the IP owner of that medium, a household name brand in music, and one of the nation's largest music retailers all seem to be allied.

Meanwhile, some observers are questioning whether this new approach to selling music will appeal to either remaining buyers of music CDs or the generally younger users who are accustomed to downloading MP3 songs, often free of charge. As analysts have noted before, especially for BetaNews, CDs and MP3s constitute very different sides of the music market.

By and large, MP3 downloads are most popular among teenagers. Further, many of those teens are downloading the songs on to portable devices from Apple, said Mark Best, an analyst at JupiterMedia, in an earlier interview.

"But adults still tend to like to have something they can hold in their hands, and they like to 'own' their music," he added. In many instances, digital downloads constitute more of a "rental" than an "ownership" model, according to the analyst.

SanDisk hasn't yet specified pricing for the slotMusic music cards, and the "big four" records labels haven't announced how many titles they plan to release on slotMusic cards.

SanDisk's earlier "gruvi" -- an effort launched in 2005 which failed to grab hold -- called for selling preloaded music and video on flash memory cards that could also accommodate downloaded content. The gruvi cards carried a steep suggested retail price of $39.99, however. And unlike the DRM-free slotMusic service, the gruvi cards came with their own DRM, although gruvi content could be moved around between devices.