 There have been other timpani concertos, notably, Philip Glass, considered one of the most influential composers of the late 20th century, wrote a double concerto at the behest of soloist Jonathan Haas titled "Concerto Fantasy for Two Timpanists and Orchestra", which features its soloists playing nine drums a piece.For general playing, a timpanist will beat the head approximately in from the edge.Beating at this spot produces the round, resonant sound commonly associated with timpani.