What Are Intervals?

Semitones and whole steps

The smallest interval in western music is a semitone, also called a half step. On guitar, moving up or down one fret is exactly one semitone. Two frets is two semitones, also called a whole step or whole tone.

Every interval is measured in semitones. A minor 3rd is 3 semitones. A perfect 5th is 7 semitones. Once you know how many semitones an interval spans, you can find it anywhere on the fretboard by counting frets.

The 12 intervals

Within one octave there are 12 unique pitches and 12 intervals, one for each semitone. Each has a name and a characteristic sound. These names come up constantly in music theory when describing scales, chords, and progressions.

Perfect, major, and minor

The naming system for intervals has two categories. Perfect intervals (unison, 4th, 5th, octave) do not have major or minor versions in the traditional sense. They are stable and symmetric. Flattening a perfect interval by a semitone makes it diminished. Sharpening it makes it augmented.

All other intervals come in major and minor versions. Major intervals are one semitone wider than their minor counterpart. The major 3rd is 4 semitones, the minor 3rd is 3. The major 6th is 9 semitones, the minor 6th is 8. This is consistent across all non-perfect intervals.

How intervals build scales and chords

A scale is a specific sequence of intervals from a root note. The major scale uses the pattern: whole, whole, half, whole, whole, whole, half. In semitones that is 2, 2, 1, 2, 2, 2, 1. Every major scale everywhere in the world uses this exact pattern of intervals starting from whatever root you choose.

A chord is built by stacking specific intervals above a root. A major chord stacks a major 3rd (4 semitones) and then a perfect 5th (7 semitones from the root). A minor chord stacks a minor 3rd (3 semitones) and a perfect 5th. One interval changes, and the entire emotional quality of the chord changes with it.

Intervals on the guitar neck

On guitar, the same interval always looks the same relative to any starting note. A perfect 5th is always 2 strings up and 2 frets up (on strings 6 to 4 or 5 to 3). A minor 3rd is always 1 string up and 2 frets down. These shapes repeat across the whole neck.

This is one of the advantages of the guitar. Once you learn what an interval looks and sounds like in one location, you can find it everywhere. Scales and chords become patterns of intervals rather than disconnected collections of finger positions.

Ear training with intervals

The most practical skill you can build is recognizing intervals by ear. When you hear a melody or a chord, intervals are what your ear is actually processing. Knowing that a minor 3rd sounds like the opening of a particular song, or that a tritone creates maximum tension, makes you a faster and more musical player.

Start with the most distinctive ones: the octave (instant recognition), the tritone (unmistakably tense), and the perfect 5th (open and powerful). From there, work on the 3rds, which are the most emotionally loaded intervals in all of western music.