...has been annoying the daylights out of you by appearing all the time on the music channels, check this out. This is twisted beyond compare. Lady GaGa (really) plays the piano and goes apeshit.
I think she kind of just bangs the piano at random (occasionally taking care to hit the right chord) and singing away. Either that, or she's a secret genius pianist and I have no taste.
Especially the part where she puts her heel on the piano. She might actually be on crack, as one of the comments pointed out.