Inverting intervals
Turn an interval upside down and predict the result.
Turn an interval upside down and you get another interval, related to the first in a very regular way. On the bass this means you can always pick the closer way to reach a note.
What inversion is
Inverting an interval means moving the lower note up an octave, or the upper note down an octave. C up to G is a perfect 5th; inverted, it becomes G up to C, a perfect 4th. C up to E is a major 3rd; inverted, E up to C is a minor 6th.
Three rules
- The numbers add up to 9: 2nd ↔ 7th, 3rd ↔ 6th, 4th ↔ 5th, unison ↔ octave.
- The qualities swap: major ↔ minor, augmented ↔ diminished, and perfect stays perfect.
- The semitones add up to 12.
| Pair | Numbers | Semitones |
|---|---|---|
| P1 ↔ P8 | 1 + 8 = 9 (unison and octave) | 0 + 12 = 12 |
| M2 ↔ m7 | 2 + 7 = 9 | 2 + 10 = 12 |
| m2 ↔ M7 | 2 + 7 = 9 | 1 + 11 = 12 |
| M3 ↔ m6 | 3 + 6 = 9 | 4 + 8 = 12 |
| m3 ↔ M6 | 3 + 6 = 9 | 3 + 9 = 12 |
| P4 ↔ P5 | 4 + 5 = 9 | 5 + 7 = 12 |
| A4 ↔ d5 | 4 + 5 = 9 | 6 + 6 = 12 |
On the bass
Going up a 5th reaches the same note name as going down a 4th, and going up a 3rd is the same as going down a 6th. You can always choose the closer one.
From C at fret 3 on the A string, find E a major 3rd above, then the E a minor 6th below. Repeat with D: a major 2nd up, a minor 7th down.