We have a "piano cat" too -- Only one of the four cats "plays" so we always know it's Sammy when ramdom music starts (at odd times).

I think it's odd that only ONE of them is attracted to the piano (since cats always want to be on stuff that you don't really want them on!).

I used to have one cat that would come and sit on the bench with me anytime I played. After a few minutes, she would help by pawing the notes in front of her.