Intervals

Semitones and tones

An interval is the distance between two notes. The smallest distance in Western music is the semitone (half step), and two semitones make a tone (whole step).

Learning to count semitones is the key to naming intervals correctly, because two intervals can look similar on the stave but contain a different number of semitones.

Interval number

The number of an interval is found by counting letter names, including both the bottom and the top note. F to G is a 2nd, F to A is a 3rd, and so on.

A note with itself is a unison (1st), and the same letter eight notes higher is an octave (8th).

Interval quality

The quality tells you the exact size. Unisons, 4ths, 5ths and octaves can be perfect. 2nds, 3rds, 6ths and 7ths can be major or minor, and a minor interval is one semitone smaller than a major one.

An augmented interval is one semitone larger than a perfect or major interval. A diminished interval is one semitone smaller than a perfect or minor interval.

Intervals up to the octave

This site uses P for perfect, M for major, m for minor, A for augmented and d for diminished. Some books write ma and mi instead of M and m, or + and o instead of A and d. Some intervals share the same number of semitones but have different names, such as the augmented 4th and the diminished 5th.

Inverting intervals

To invert an interval, move the bottom note up an octave so it becomes the top note. For example, C up to E (a major 3rd) becomes E up to C (a minor 6th).

There are simple rules for what happens when you invert.

• The two numbers always add up to 9: a 2nd becomes a 7th, a 3rd becomes a 6th, a 4th becomes a 5th.
• Perfect stays perfect.
• Major becomes minor, and minor becomes major.
• Augmented becomes diminished, and diminished becomes augmented.