background music manager not working correctly

Hi, I was wondering if I could get some help making a basic audio manager. I have three different parts to the same song that I want to use (A beginning, a middle, and an end). I want to set it up in such a way so that on the title screen the manager plays the beginning then goes straight to the middle and loops the middle until you press the start/play button. after you press the play button I want it to stop looping the middle but finish playing it then I want it to play the end. pressing play does in fact change the scene and I want the transition to be as seamless as possible (both in the transition between tracks and in the scene)

nothing yet?