Inverting intervals
Invert an interval and use the rule: the numbers add up to nine, and the quality turns into its opposite.
Turning an interval over
To invert an interval is to move its bottom note up an octave (or its top note down an octave). The notes stay the same, but the interval between them changes.
The third C–E, inverted, becomes the sixth E–C. The fifth D–A becomes the fourth A–D.
major third and its inversion minor sixth; perfect fifth and its inversion perfect fourth
Practice: Inverting a third
Practice: Inverting a fifth
The rule of nine
An interval and its inversion add up to an octave, so:
- The numbers add up to 9: second ↔ seventh (2 + 7), third ↔ sixth (3 + 6), fourth ↔ fifth (4 + 5), unison ↔ octave (1 + 8).
- The quality turns into its opposite: minor ↔ major, augmented ↔ diminished. Perfect stays perfect.
Interval Inversion
minor third major sixth major second minor seventh perfect fourth perfect fifth augmented fourth diminished fifth augmented second diminished seventh
The rule helps build "hard" intervals downward. Need a major sixth below E? Build a minor third above E (G) and move it down an octave: the sixth below E is G.