Scott Joplin ;)

DUMB Odysseyware Cheaters

http://en.wikipedia.org/wiki/Five_Pieces_for_Orchestra

Arnold Schoenberg ;)

Claude Debussy is accredited with creating music which was devoid of a particular harmonic tonal center, however Schoenberg may perhaps be considered the first "atonal" composer. He wrote music in an attempt to give "equal value" to all 12 tones. He wrotePierrot Lunaire which is considered one of the first pieces completely atonal.

A typical orchestra concert will contain pieces such as a symphony, a concerto, and perhaps an overture.