The orchestra frequently includes two clarinetists playing individual parts—each player is usually equipped with a pair of standard clarinets in B and A, and clarinet parts commonly alternate between B and A instruments several times over the course of a piece, or less commonly, a movement (e.g., 1st movement Brahms' 3rd symphony). Clarinet sections grew larger during the last few decades of the 19th century, often employing a third clarinetist, an E or a bass clarinet. In the 20th century, composers such as Igor Stravinsky, Richard Strauss, Gustav Mahler, and Olivier Messiaen enlarged the clarinet section on occasion to up to nine players, employing many different clarinets including the E or D soprano clarinets, basset horn, alto clarinet, bass clarinet, and/or contrabass clarinet.