The word ‘diatonic’ can be used to describe both scales and harmony. Scales are considered to be a series of single notes moving either up or down. When we refer to harmony, the reference is towards chords; these are usually three or more notes played together. It is important to make this distinction before going further into the concept of diatonic music as it can be a point of confusion.
Like many musical terms, the word ‘diatonic’ has its origins in Ancient Greek. The first part of the word ‘dia’ loosely translated means ‘across’ or ‘through’ giving the whole word the meaning of ‘through a key centre’. When we discuss anything related to diatonic it is essentially ‘key’ related. By this, I mean C major or Eb minor as a key in which the diatonic scale and harmony are created.
The important element to grasp here is that we are only considering the seven notes of a scale, not the chromatic alternative. If we begin on the note ‘C’, then this would present us with the following notes: C, D, E, F, G, A, B. Note there are no ‘black’ notes included here as they would not be part of a C major scale which is what I have written out above. What you may already be able to see is that the idea of diatonic music must include the early idea of ‘modality’ that stretches back many hundreds of years and was an established scalic and harmonic system way before tonality.
In contrast, the ‘chromatic scale’ includes every note across an octave, or further. It moves by semi-tone rather than tone and is perhaps understandable then that the Greek word ‘chromo’ that means colour is part of the description of the scale.
The chromatic scale then leads us down the tonal route as opposed to the diatonic as it covers every possible tonal key with the possibility of a re-organization of pitches that can create exotic scales such as the whole-tone.
A closer analysis of the diatonic scale from above shows that the arrangement of tones and semi-tones is a follows; tone, tone, semi-tone, tone, tone, tone, semi-tone. Remember, a tone is made up of two semi-tones (C – C# – D). This allocation of tones and semi-tones remains the same regardless of the starting note; assuming we are working around the white notes of the piano.
For example, if you begin the diatonic scale on an ‘E’ (E, F, G, A, B, C, D), there are still five tones and two semitones in the scale, they just appear in a different order. It also means that the scale contains no other ‘alterations’ to is in terms of additional sharps and flats.
This means that any major scale can be thought of as a diatonic scale as none of the tones in that scale is altered and it neatly fits the pattern tones and semi-tones discussed above. What this also means is that some of the minor scales can be considered to be diatonic too. Minor scales are a little more complicated and fall into three categories.
There are three kinds of minor scales. These are called the harmonic, melodic and natural minors. The harmonic minor is a curiosity as it includes the interval of a minor third which gives it its distinctive sound. Starting on ‘C’, then the harmonic minor would comprise of the following notes: C, D, Eb, F, G, Ab, B). This interval of a minor third (Ab – B), is not one included in the diatonic pattern and so the harmonic minor cannot be considered to be a diatonic scale.
Equally, the melodic minor presents a different picture. (Ascending – C, D, Eb, F, G, A, B and descending – C, Bb, Ab, G, F, Eb, D, C). Note that the scale is different ascending as it is descending. The reasons for this stem from the earlier modal system, but if you look closely at the number of tones and semi-tones, they match the diatonic model and therefore can be included in that harmonic framework.
Lastly, we must focus on the ‘natural’ minor scale. This scale sounds more ‘modal’ than perhaps any of the other scalic forms. The way by which the scale is constructed is achieved by simply playing the notes of the scale including the accidentals that may or may not be in the key signature. Using ‘C’ as a starting not again, this would effectively give us a scale that consisted of the following notes: C, D, Eb, F, G, Ab, Bb and C. The ascending scale would be exactly the same as the descending scale and aligns with the diatonic model.
Harmony can also be based on the diatonic principles we have examined. Harmony is broadly speaking, the scaffolding that supports the melody. It is the vertical whereas the melody is horizontal, to give another musical picture to think about. If we return to C (major), for a moment, then we can build a harmonic picture from each of the notes of that scale. This gives an array of chords that encompass both major, minor and diminished.
This is how the range of chords would emerge from the ascending scale with C as a starting note: C major, D minor, E minor, F major, G major, A minor, B diminished. Each of these chords can be successfully used to support a diatonic melody. It is, of course, possible to write a diatonic melody and use a chromatic chordal pattern, or other non-diatonic selection of chords but then the entire composition is no longer purely diatonic.
One memorable and a rather beautiful example of diatonic music is the Shaker tune ‘Simple Gifts’. Like many melodies that are often classed as ‘folk’, there is a tendency to write diatonically. The shaker melody is purely diatonic and effortlessly encapsulates the modest nature of these people.
The American composer Aaron Copland incorporates this tune in his ‘Appalachian Spring Suite’ in a way that makes it sound as if it has sprung from the pen of the composer himself. Harmonically and melodically, this gentle piece of music is a great way of ending the article and inspiring you to explore the idea of diatonic music further.