so you want a sound track that follows the frames, but doesn't get ahead of or behind them, right?
Why not use a repeating audio track for eac frame that you can turn off and play a transition piece through the frame transition to the next audio file?
Shouldn't be that hard to do. Also, you can just use the transition function to play a clip of audio that you want for this. The clip should be repeating so that it dont' end, ie, it's a lot longer than you will ever need. Make it 5 minutes for a 1 minute slide. That way you never run out of audio.
I've done these a few times, so if you want more help, just ask.