Fifth complement

Analogous to the octave complement, the fifth complement of a given fifth-reduced interval is its interval distance from the perfect fifth (3/2). It seems to be very useful as a way of conceptualizing and constructing traditional-sounding tertian triads, and even as a way of describing the relationships between different thirds.

History

The idea that the major third and the minor third complement or contrast each other may date well back to the Classical period, when tertian triads, in the form of root–third–fifth, dominated the construction of chords. The term was seemingly coined by Flora Canou in September 2020.

Examples

The following interval pairs are fifth complementary to each other:

• 5/4 and 6/5
• 19/16 and 24/19
• 9/8 and 4/3

See also

• Octave complement
• Twelfth complement
• Fourth complement