Perfect fifth

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In Western music theory, a perfect fifth (abbreviated P5) is a musical interval corresponding to a pair of pitches with a frequency ratio of 3:2, or very nearly so. A fifth is an interval spanning five staff positions. The diminished fifth and augmented fifth are one chromatic semitone narrower and wider than the perfect fifth respectively. The perfect fifth spans seven semitones in equal temperament. For example, the interval from C to G is a perfect fifth, as it spans five staff positions and G lies seven semitones above C. The perfect fifth may be derived from the harmonic series as the interval between the second and third harmonics. In a diatonic scale, the dominant note is a perfect fifth above the tonic note. The perfect fifth is more consonant, or stable, than any other interval except the unison and the octave. It occurs above the root of all major and minor chords (triads) and their extensions. Until the late 19th century, it was often referred to by one of its Greek names,...

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