Here’s Elliott Carter’s Eight Pieces for Four Timpani written between 1950-66 for eight different percussionists. Very impressive piece of music, I’ve learned about it just today after a percussion seminar. Also you’d love to see the performance DVD by the percussionist Dr. Stuart Marrs, a very good timpanist and interpretation is very impressive.

PS: You can listen to the whole piece clicking videos on the right side menu of youtube.