Inversion of Intervals
Flipping intervals upside down.
Flipping the Notes
An inversion is created by moving the lower note of an interval up an octave, or the upper note down an octave.
The Rule of Nine
When you invert an interval, the sum of the original number and the inverted number always equals nine (e.g., a 2nd becomes a 7th).
Quality Mirroring
Major intervals invert to minor, perfect to perfect, augmented to diminished, and vice versa.
Summary
Interval inversions help you recognize intervals and understand voice leading in chord progressions.