Intervals

An interval is the distance between two notes. Once you can hear and name intervals, melodies stop being a blur of pitches and start making sense: you recognise the familiar jumps that songs are built from. Every interval has a two-part name, and both parts matter.

Part one: the number

The number comes from counting letter names inclusively, starting on the lower note as "one". From C to E you count C-D-E, three letters, so that is a 3rd. From C to G you count C-D-E-F-G, five letters, so that is a 5th. The same note played twice is a unison, and eight letters up (C to the next C) is an octave.

Part two: the quality

The number alone is not precise, because a "3rd" can be slightly wider or narrower. The quality fixes the exact size by counting semitones (the smallest step on the piano, from any key to the very next key). Some intervals are called perfect, and others are major or minor:

• 4ths, 5ths and octaves (and the unison) are called perfect.
• 2nds, 3rds, 6ths and 7ths come in major and minor forms, where minor is one semitone smaller than major.

There is also the tritone, sitting exactly halfway across the octave at six semitones. It can be written as an augmented 4th or a diminished 5th.

The common intervals, and songs to hear them

The fastest way to learn intervals is to tie each one to a tune you already know. Here are the common intervals within an octave, ascending from a starting note:

Train your ear

Recognising intervals by sound is a skill you build through repetition. The trainer below plays two notes; your job is to name the interval between them. Start with the easy landmarks (the perfect 5th and the octave), then add the 3rds, and work up from there. A few minutes a day adds up quickly.

Naming an interval is two steps: count the letters for the number, then count the semitones for the quality. Learn a reference song for each one, and soon you will hear them in the music you already love.