You don't need to do anything. Just press the green flag and listen! Just an answer to a question on the "help with scripts" forum.
I found a way to sync costume changes (or sounds) with the beat of the song. I run a routine that captures the beats that I tap on the Spacebar. Then I change costumes (or play another sound) when each recorded, elapsed time comes up. Compare it to the original (which is actually very well synced, but not perfect).
