I see that you have not yet received an answer about your issue trying to play music as your iPhone alarm. Some additional information could provide helpful to others in determing how they can best help. Some information could be:
1. Are you able to select an alarm sound from the system provided sounds? Does that sound work? 2. Does the music you selected for your alarm play in the Music app? 3. Have you tried a different song? 4. What troubleshooting steps have you already tried?