Hey Steve!
Generally speaking I love the idea, and I also like rythm games, so this was a great match. With this one it felt like it's harder to get the first bucket-pass than to get the upcoming ones, but maybe it was just my lack of rythmic understanding. So after I did the first 2-3 passes, I usually was able to finish the whole loop.
It is also a great touch that you let the player know if they were early or late. Did you try to make it somewhat of a "real-time feedback", so players can see right away if they were early? Maybe that could also work.:)
Great entry all in all, cheers