UK music download retailer 7digital has beaten Spotify to launching in the U.S., in a move that undercuts standard iTunes track prices. The service has repertoire from all four major labels and a range of indies and is using a new BlackBerry service as a springboard for the move.The company, which HMV (LSE: HMV) bought 50 percent of from VCs last month, first revealed its American ambition to paidContent:UK a year ago. Now, after inking the label deals, it is launching there with standard tracks at $0.77 (iTunes charges $0.69 for older songs, $0.99 for recent tracks and $1.29 for new hits).Listen!