Interval
An interval is the distance in pitch between two notes, named by a number that counts letter names, such as a third or a fifth, and a quality that fixes its exact size in semitones.
How do you name an interval on real notes?
Two counts, always.
- The number counts letter names, both ends included. C up to E is C–D–E, three letters: a third. C up to G is five letters: a fifth.
- The quality counts semitones. C to E is 4 semitones, a major third. C to E♭ is 3, a minor third. C to G is 7, a perfect fifth.
| Interval | Semitones | From C |
|---|---|---|
| Minor second | 1 | C–D♭ |
| Major second | 2 | C–D |
| Minor third | 3 | C–E♭ |
| Major third | 4 | C–E |
| Perfect fourth | 5 | C–F |
| Tritone | 6 | C–F♯ or C–G♭ |
| Perfect fifth | 7 | C–G |
| Minor sixth | 8 | C–A♭ |
| Major sixth | 9 | C–A |
| Minor seventh | 10 | C–B♭ |
| Major seventh | 11 | C–B |
| Octave | 12 | C–C |
How do you recognise an interval by ear?
Hear its character, not its size. A major third sounds bright and settled, a minor third darker, a perfect fifth open and hollow, a tritone unstable.
Many people start with a song they know by heart. “Greensleeves” opens with a rising minor third. “When the Saints Go Marching In” opens with a rising major third. The song is scaffolding: the goal is to recognise the interval before the song comes to mind.
The same interval also arrives in different forms: melodic (one note after the other, up or down) or harmonic (both at once). Each form is worth practising.
Why is C to E a third and not a fourth?
Because the first letter counts as one. Counting semitones starts from zero, so C to E is 4 semitones but only a third. Mixing up the two counts is the most common interval mistake.
The spelling matters too. C–D♯ and C–E♭ are both 3 semitones, but C–D♯ spans two letters, so it is an augmented second, not a minor third.
Try it: Intervals by Ear plays two notes and asks you to name the distance between them.