noun MusicThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Modification of the intervals of just intonation in the tuning of instruments of fixed intonation to permit harmonic modulation. It allows one to modulate to or play in any of the 12 major or 12 minor keys.