Animusic(Edit)
You seens this?
In my opinion they must use a technique similar to what I was saying where you parse something richer than audio data, such as a .mid file.
Floating Custom Bone(Edit)
See the left side, where the custom bone shape is circled? Also, see how all the bones are in a line.
Now look at the one on the right. The first bone is up in the air, where it shouldn't be, even though the others are in place. It's not a bone roll issue.