well, as i've said many a time, select the layer with the music in, go to property's and then there is a box, select the sound that you are using, and there is another box, select stop.
nah i figured it out....it was because the song was longer than the amount of frames...... so the song carried on whilst the frames restarted...when the frames restarted the song restarted whilst the original song was still playing...