n. The use of multiple keys in the same composition, especially by multiple instruments at the same time
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. music that uses two or more different keys at the same time
Word Usage
"By the late 1940s, he was already employing modern classical ideas such as polytonality and dissonance, and working in unusual time signatures to create a distinctive jazz sound."