perfect fifth

The perfect fifth or diapente (sometimes abbreviated P5) is a musical interval which is responsible for the most consonant, or stable, harmony outside of the unison and octave. It is a valuable interval in chord structure, song development, and western tuning systems. The prefix perfect identifies it as belonging to the group of perfect intervals (perfect fourth, perfect octave) so called because of their extremely simple pitch relationships resulting in a high degree of consonance.
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