Definition of "octave" []

• Music The interval of eight diatonic degrees between two tones of the same name, the higher of which has twice as many vibrations per second as the lower. (noun)
• Music A tone that is eight diatonic degrees above or below another given tone. (noun)
• Music Two tones eight diatonic degrees apart that are sounded together. (noun)
• Music The consonance that results when two tones eight diatonic degrees apart are sounded. (noun)
• Music A series of tones included within this interval or the keys of an instrument that produce such a series. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The same Mass has Dies Irae sung in octave alternation."
• "Note also that an octave is the difference between a harmonic and the adjacent harmonic (the frequency of one octave up is 2x the frequency of the fundamental)."
• "Dies Irae was sung in octave alternatim by 250 people to create a beauty of enormous power."