Theory · glossary
Interval
Also called musical interval, pitch interval
An interval is the distance in pitch between two notes. Its size is counted in semitones and its name comes from the letter names it spans: C up to E covers C, D and E, so it is a third, and at 4 semitones it is a major third.
An interval’s name has two parts. The number counts letter names, including both ends: C, D, E is three letters, so C to E is a third. The quality (major, minor, perfect, augmented or diminished) comes from the exact number of semitones. C to E is 4 semitones, a major third. C to Eb is 3, a minor third.
Here are the intervals from C up to the next C:
| C up to | Semitones | Name |
|---|---|---|
| Db | 1 | Minor second |
| D | 2 | Major second |
| Eb | 3 | Minor third |
| E | 4 | Major third |
| F | 5 | Perfect fourth |
| F# | 6 | Tritone (augmented fourth) |
| G | 7 | Perfect fifth |
| Ab | 8 | Minor sixth |
| A | 9 | Major sixth |
| Bb | 10 | Minor seventh |
| B | 11 | Major seventh |
| C | 12 | Octave |
The names work the same whether the two notes sound together (a harmonic interval) or one after the other (a melodic interval).
An octave sounds like the same note, higher, because the frequency doubles: A4 is 440 Hz and A5 is 880 Hz. A perfect fifth sounds open and stable, and a power chord is a root and its fifth, often with the octave on top. A major third sounds bright and a minor third darker. A minor second rubs, and so does a tritone. The B and F inside a G7 chord are a tritone apart, and they pull toward C major: B rises to C and F falls to E.
Chords are stacks of intervals. A C major triad, C E G, is a major third (C to E) with a minor third on top (E to G), and the outer notes, C to G, make a perfect fifth. Put the minor third on the bottom and you get C minor, C Eb G.
Chord symbols count intervals above the root. The 5 in C5 is the fifth, G, and the 7 in C7 is a minor seventh, Bb. The 9 in Cadd9 is a ninth, D, an interval wider than an octave: C up to the D above the next C is 14 semitones. How to read chord symbols decodes the rest of those numbers, and what notes sound good together covers which intervals clash.
Updated . All terms · Try the online chord pads