After years of selling digital music with restrictive copy-protection technology, major music labels are beginning to make some songs available as unrestricted MP3 files. “The releases are part of an experiment to gauge demand for tracks that can be played on any digital music player capable of playing MP3s,” reports the Associated Press. “Normally, copy-protected tracks are only playable on certain devices. By selling MP3s, recording companies can ensure they can be played on Apple’s market-leading iPod players without going through Apple’s iTunes Music Store.” The latest unrestricted MP3 tracks come from singer Norah Jones and rock band Relient K, both signed to labels operated by Britain’s EMI Music. Their songs went on sale for 99 cents each this week on Yahoo’s online music service.