Compound Intervals

In the major scale, all of the steps of the scale are related to scale degree 1 by a major or perfect interval:

That means, that if you know your major scales, you can use your know-how to build any major or perfect interval you want by simply imagining constructing the major scale above that note, or using the key signature of that scale to adjust the accidental as necessary. See the steps below:

We can think of all of the other intervals as variations on the Major or Perfect intervals. For any given interval (e.g. m6), start by building the major or perfect interval first (e.g. M6), then adjust the accidental by moving it up or down to make it augmented, minor, or diminished. See the steps below:

Note: When you adjust the accidental to change the quality of the interval, do not change the letter name of the note or you will alter the size of the interval (e.g. lower G to Gb, but not to F#).

To construct an interval below a given note, start by determining the inversion of the interval:

Then, follow the steps below to construct a descending interval:

Compound intervals are intervals that are greater than an octave.

It is easiest to spell and identify compound intervals by thinking about their "simple" variant. For instance, a M9 interval is C to D, if you reduce that to less than an octave, you have a M2.

Compound intervals are always related to their simple interval by 7. If you subtract 7 from any compound interval, you'll have the simple interval. If you add 7 to any simple interval, you'll have the compound interval. For example:

• A 13th is a compound 6th because 13 – 7 = 6.

• The compound form of a 5th is a 12 because 5 + 7 = 12.

Note that the compound form of the simple interval carries the quality Major or Perfect (e.g. it's a P12, not a M12).