Wal-Mart, the world's largest retailer and seller of recorded music, has started offering songs free of copy protection today at 94 cents per track. These songs include ones by the Rolling Stones, Coldplay and Maroon 5, among others, and will play on most portable media devices, including Apple Inc.'s iPod. Although many independent music labels have for years sold their tunes without copy restrictions, major recording companies have insisted on digital-rights management, or DRM, technology in hopes of curbing online piracy; DRM, however, has become a hassle for consumers, restricting where a buyer may play his or her music. Britain's EMI Group PLC earlier this year became the first of the major labels to embrace DRM-free tunes, letting Apple sell DRM-free versions of songs with higher audio quality for $1.29 per track. Wal-Mart will continue to offer WMA tracks with DRM at 88 cents.