The Diatonic Scale

Intervals between notes that form the scale of a particular key are said to be diatonic. This applies to major and minor scales. Notes that are not part of these scales are said to be chromatic - those notes are chromatic notes.

Let us look at a few examples.

In the key of C the notes C, D, E flat, E, F, G, A flat, A, B flat and B are diatonic because they appear in one or more of the major, natural minor, melodic minor or harmonic minor scales. In this key, any other note will be chromatic.

When examining the relationship between notes, the key is a vital element. In the key of C, D sharp will be a chromatic note. However, in the key of E, both C and D sharp are diatonic because both appear in the scale of E harmonic minor.

We have more to say on this in the next lesson.

Do not confuse chromatic notes with chromatic scales. We have already met the chromatic scale, one example of a symmetrical scale, those constructed from a repeating pattern of intervals (in this case, a semitone or half-step). Some notes of a chromatic scale are chromatic to the key note (in this case the first note) while others are diatonic. We will meet other symmetrical scales in lesson 25.

The terms diatonic and chromatic can be extended to any groups of notes, musical phrases, scale passages, chords and harmonies as we shall find later. What is important is that diatonic passages tend to have a sense of key about them. When chromatic notes are introduced, the sense of key is generally weakened.

The Chromatic Scale

With the chromatic scale there is no widely used notational 'convention' and problems occur when chromatic scale progressions occur within pieces of music in different keys. There is no universal notation that remains unvaried as one moves from key to key. Composers have been strikingly inconsistent in this area. It has been left to music theorists to offer various suggestions but, in general, composers have ignored them.

Two types of chromatic scale have been suggested, the harmonic and the melodic.

The Harmonic Chromatic Scale

The harmonic chromatic scale is the same whether rising or falling and includes all the notes in the major, harmonic minor or melodic minor scales plus flattened second and sharpened fourth degrees. This leads to a single fifth, single tonic key-note, single octave key-note and pairs of every other degree. This means that the notation of a harmonic chromatic scale varies according to the key signature.

We give an example below - the harmonic chromatic scale in C.

To listen to the harmonic chromatic scale in C press the play button displayed below.

The Melodic Chromatic Scale

The melodic chromatic scale is more problematic because there is a general lack of agreement as to how it should be written. As with any chromatic scale, the interval between successive notes is a semitone. The way the notes are written, however, is left to personal taste, and, for this reason, we have given no example. In every case, the ascending and descending versions are different (for example, the rising scale might be written with naturals and sharps while the falling scale is written with naturals and flats) and they will vary according to whether the key is major or minor. The main notes are still drawn from all the notes of the major and both minor scales. To find the remaining notes, the only clear rule is that no note name should be used more than twice in succession and that the first, fifth and eighth degrees can be repeated.