Alas, there is not currently a rock-solid timing mechanism for music and audio playback to a tempo. The suggestion of timers is a good one; we used a system like this on Bulletstorm to allow branching on a measure-by-measure basis. This was done at the C++ level though. Audio will at some point get its own thread, at which point this functionality will be possible natively. Sorry I couldn’t be of more help.
Best-
Zak