This page is about intervals in music. What does that even mean? What is an interval in music? That’s in the middle of the performance right? When everyone takes a break for twenty minutes?

Well, no. That’s a different type of interval.

An interval is defined as the distance between two notes, either sounded simultaneously (harmonic interval) or one after the other (melodic interval).

Sounds easy! How can we measure musical intervals? Can we use a ruler or a tape measure?

Unfortunately no but the lines and spaces of the stave do give us a useful measuring tool. Also, when we use a ruler we start counting at 0 but when we count intervals we start at 1. Let’s see why.

You will remember that all major and minor scales must use each letter name note in succession with the notes placed on alternate lines and spaces.

Here is the scale of C major:

If we take each note of the major scale and play it against the tonic note, C, we get all the major and perfect intervals.

Two notes at the same pitch are called unison (meaning “one sound”).

An eighth is called an “octave”.

All intervals of a second will lie on adjacent lines and spaces (line to space or space to line).

All intervals of a third will lie either on the next adjacent line or space (line to line or space to space).

Lowering a major interval by a semitone produces a minor interval.

Raising a major interval by a semitone produces an augmented interval

Although augmented seconds and minor thirds sound the same they are different intervals in theory and are likely to have different harmonic functions. They are said to be “enharmonic” which means that they sound the same. Can you find any other enharmonic intervals?

Inverting a major interval produces a minor interval (and vice versa):

Lowering a perfect interval by a semitone produces a diminished interval.

Raising a perfect interval by a semitone produces an augmented interval.

Inverting a perfect interval produces another perfect interval!

Now compare the intervals of the descending major scale with the ascending ones we began with. All the perfect intervals stay the same but the major intervals become minor.

How can I work out any interval?

Method 1 Counting Semitones

Since the semitone is our smallest interval in most western classical music and certainly on the keyboard, it makes sense to count the number of semitones between notes to establish the interval. But remember that a semitone is the smallest interval between one note and the one next to it. You have to count all the black notes as well as the white ones.

Let’s take the third as an example. A minor third is constructed of 3 semitone steps.

So for example the interval between E and G consists of three semitone steps, E to F, F to F# and F# to G. This means that it is a minor third.

The Major third is constructed of four semitones. It is also constructed of two whole tones.

The problem with this method is that there is no distinction between enharmonic intervals. Ie. a minor third has the same number of semitones as an augmented second. It also becomes more prone to accidents of calculation as the intervals get wider.

Method 2 Diatonic relationship to the lower note.

In this method you first examine the position of the two notes on the stave.

Now assume the lower note is the tonic (even if it’s not) and find out if the upper note is diatonic in the major scale starting on that note. You can use tone tone semitone tone tone tone semitone if you don’t know your key signatures.

That sounds more complicated than it is! So, let’s take the notes D and A for example.

We can see that the two notes are two spaces apart making them a fifth. In D major, A is the fifth note (D, E, F#, G, A) so this must be a perfect fifth.

Here’s another example. The notes are F and B.

We can see that the two notes are one space and on line apart making them a fourth. The fourth note in F major is Bb but this is B natural – a semitone higher – so it must be an augmented fourth.

Here are some more intervals for you to work out: