What is a perfect fifth in music?
A perfect fifth is an interval that spans seven half steps. You can think of it as the distance from the tonic, or first note of a scale, up to the fifth note of the scale. The perfect fifth also forms the outline of
major and minor triads. It is one of the most consonant intervals in music and gives major and minor chords their stability.
Why does a perfect fifth sound so good?
A perfect fifth is satisfying to our ears because its two tones form a pleasing harmonic ratio, 3:2. This means the upper note in a perfect fifth has a frequency one and a half times higher than the lower note. The harmonics, or overtones, of the two notes line up together in a series that doesn’t clash. This gives it an open, hollow quality that can sound rather ambiguous. When you hear the two notes of a perfect fifth, you can’t tell if the chord it outlines is major or minor.
What are examples of a perfect fifth on piano?
C up to G is a great example of a perfect fifth on a piano. Another example would be G up to D, or E♭ up to B♭.
Why are some intervals called perfect?
The musical term “perfect” is reserved for intervals whose frequency ratios are simple and involve small numbers (2:1, 3:2, and 4:3 for perfect octaves, perfect fifths, and perfect fourths, respectively). These ratios result in very stable, consonant sounds, unlike the imperfect consonance of thirds and sixths, or the outright dissonance of seconds and sevenths. The music of many ancient cultures, including Greek and Chinese, recognized the beauty of perfect intervals and built their
musical scales around them.
What is the relationship between the perfect fifth and the circle of fifths in music?
The circle of fifths is built entirely from perfect fifths. When we organize scales with the tonic (first note) of each scale a perfect fifth higher than the last, we start with C (no sharps) and add one sharp to each scale until we have a scale with all seven notes sharp. On the other hand, starting each scale a perfect fifth lower than the last adds flats until all the notes of the scale are flat. So the circle of fifths gives us a methodical tool for organizing all the sharp and flat scales.
The circle of fifths also relates each adjacent scale by the interval of the perfect fifth, which is foundational in music. Any two chords built a perfect fifth apart will have a dominant to tonic relationship, which is the strongest chord progression available. The circle of fifths is therefore used to identify which keys have this important relation with each other.
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