Extending the Animation / Keyframes tool

I haven't found doing something like this before, and I don't know where to start.

I'd like to use the animation window and keyframes to sync events to music easily, like I would in a music program. To do this I want to define a tempo, and then replace the time with beats and bars, so my event keyframes can snap to the beat.

How would I go about this? I don't even know how to get the base code for the animation / keyframes window, to let me start to modify it. Thanks to anyone who can help.