Understanding Intervals

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Understanding intervals is a vital key to unlocking the mysteries of music theory.

An interval always concerns two notes.

Interval names have two parts: a number (from 1 to 13) and a type. Special names are given to the number 1 and 8 intervals (unison and octave).

The number part of the interval name always refers to where the notes are found on the Major Scale if you consider the lowest note in the interval to be the key note.

For example the interval C to E is a 3rd because in the C major scale E is the third note.

The unison, 4th, 5th and Octave intervals are described as 'perfect'.* All other intervals on the major scale (2nd, 3rd, 6th and 7th) are called 'major'

If you reduce a major interval by one semitone it is called 'minor' If you reduce a perfect or minor interval by a semitone it is called 'diminished' If you increase a perfect or major interval by a semitone it is called 'augmented'

So here are the intervals from the note C in order of magnitude:

C to C = Unison
C to Db = minor 2nd
C to D = major 2nd
C to Eb = minor 3rd
C to E = major 3rd
C to F = perfect 4th
C to F# = augmented 4th
C to Gb = diminished 5th
C to G = perfect 5th
C to G# = augmented 5th
C to Ab = minor 6th
C to A = major 6th
C to Bbb = diminished 7th
C to Bb = minor 7th
C to B = major 7th
C to C1 = perfect Octave

This is a brief look at quite a complex part of the subject. Some bits of it may seem a little odd (Bbb for example), but these become clearer as you study chord construction theory.

*The reasoning behind the use of the word 'perfect' is researchable via this site which we recommend you visit.

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