It is not uncommon for contemporary composers to use unconventional instruments, including various synthesizers, to achieve desired effects. Many, however, find more conventional orchestral configuration to provide better possibilities for color and depth. Composers like John Adams often employ Romantic-size orchestras, as in Adams' opera "Nixon in China"; Philip Glass and others may be more free, yet still identify size-boundaries. Glass in particular has recently turned to conventional orchestras in works like the "Concerto for Cello and Orchestra" and the Violin Concerto No. 2.