An interval is the distance in pitch between two notes. Understanding intervals is one of the most important steps in learning music theory — they are the building blocks of scales, chords, and melodies.
How Intervals Are Measured
Intervals are measured in semitones (also called half steps). A semitone is the smallest interval in Western music — the distance from one piano key to the very next key, whether black or white.
Interval Names
Each interval has a specific name based on its size:
- Unison — 0 semitones (the same note)
- Minor 2nd — 1 semitone
- Major 2nd — 2 semitones
- Minor 3rd — 3 semitones
- Major 3rd — 4 semitones
- Perfect 4th — 5 semitones
- Tritone — 6 semitones
- Perfect 5th — 7 semitones
- Minor 6th — 8 semitones
- Major 6th — 9 semitones
- Minor 7th — 10 semitones
- Major 7th — 11 semitones
- Octave — 12 semitones
Melodic vs Harmonic Intervals
A melodic interval is when two notes are played one after the other (in sequence). A harmonic interval is when two notes are played at the same time (simultaneously).
Why Intervals Matter
Once you understand intervals, you can figure out any scale, any chord, and any melody simply by counting semitones. They are the underlying logic of all Western music.