Count Tom Petty and the Heartbreakers as the latest artist to test the market for MP3 sound files, as the group has taken to the web to premiere a new song, entitled "Free Girl Now," from its upcoming album, "Echo."Even though the new record isn't due out until next month, Petty is making the track available for free via the popular MP3.com site, an agreement that apparently has the blessing of Petty's label, Warner Bros. Records. "Tom Petty has always been very conscientious of his fans and their needs," a spokesman for Petty said in a statement. "Clearly, there was no other choice than to utilize the power of MP3.com as they remain the leader in music [distribution] on the world wide web." Tom Petty and the Heartbreaker's new "Echo" album is due in stores on April 13, after which the free sound file of "Free Girl Now" is expected to be removed from the MP3.com site.