Skip to content


Created: 2017-11-28 17:44:02 -0800 Modified: 2017-12-19 16:10:41 -0800

If you have an ascending interval and you want to find the corresponding descending interval, you can invert the quality and subtract from 9. For example, C to E is a major third, so E to C has to invert the quality to minor, and it’s 9-3=6. So E to C is a minor sixth.

Just add or subtract seven from the interval. For example, C to E is a major third. C to E an octave higher is 3+7=10, so it’s a major tenth.

Intervals are all a set amount of half steps, so sometimes it’s easier to just count them. For example, if you want the interval between F# and D, you know it’s a sixth since F and D are six keys apart, but if the quality is tough to figure out, you can just count that there are 8 half steps, so it must be a minor sixth rather than a major one.

This is most helpful for small amounts of half steps. For example, Fb to Gbb is a second, and they’re one half step apart, so it’s a minor second. Using our inversion trick from above, Ab to G is an ascending seventh, which means it’s also a descending second. There’s only one half step between them, so it must be a minor second, which means it’s inverted to be a major seventh ascending.

If you need to figure out C# to A#, it can be easier to just lower each one a half step so that it’s C to A. It may make it easier to see that it’s a major sixth since the key of C has no accidentals.

The couple of books that I’ve looked into have suggested this since they base intervals off of the major scale, and there are no major scales corresponding to certain notes like D#.