Symmetric

Equal division, and what it costs

Divide the octave into six equal steps and you get the whole tone scale; into four unequal but repeating pairs and you get the diminished scales; into three minor thirds with passing semitones and you get the augmented scale. In every case the same shape returns before the octave is complete, and that repetition is the defining property of the family.

The cost is tonality. A major scale tells you where home is because its intervals are unevenly spaced — the semitones act as signposts. Remove the unevenness and the signposts go with it: every note of a whole tone scale has identical neighbours, so none of them can sound like a tonic. These scales cannot establish a key, and composers reach for them precisely when they want that suspension.

Only a handful of transpositions exist

There are just two whole tone scales in all of music. Start on C and you get one set; start on D flat and you get the other; start on D and you are back in the first. The diminished scales give three distinct sets, the augmented scale four. Olivier Messiaen catalogued this property and called them modes of limited transposition, and the name describes the practical reality better than any interval formula.

For a player this is unusually good news. Learning one whole tone fingering covers half of all possible keys, and the second covers the rest. On guitar the shapes repeat every two frets — or every three, for the diminished scales — so a single pattern slides across the whole neck without ever changing.

Where each one is used

The half-whole diminished scale is the standard choice over a dominant seventh with altered extensions, especially a flat nine or sharp nine chord. The whole-half version fits a fully diminished seventh chord. The whole tone scale belongs on an augmented triad or a dominant with a raised fifth, and it carries the sound most associated with Debussy and with early film scoring for dreams and memory.

The tritone deserves separate mention because it is the smallest symmetric division of all: two notes, exactly half an octave apart. It is the interval medieval theorists called the devil in music, the axis of the tritone substitution in jazz, and the reason a dominant seventh chord wants to resolve at all.

How to use them without sounding like an exercise

Symmetric scales are the easiest to overuse, because a repeating pattern produces fluent-sounding runs with no musical decision behind them. The usual result is a phrase that clearly goes somewhere and arrives nowhere. The fix is to treat them as tension inside a progression rather than as material for a whole passage: enter on the dominant, leave on the resolution.

One practical device carries most of their use in jazz. Over a dominant chord, play the half-whole diminished scale and land on a chord tone of the chord that follows. Two bars of that teach more than a page of patterns, and it makes audible why the scale exists — it is a way of leaving the key without leaving the harmony.

Practising a shape that never changes

Because the pattern repeats, ordinary scale practice is nearly useless here: your fingers learn a loop that has no beginning. Practise sequences instead — groups of four notes moving up in minor thirds for the diminished scales, groups of three for the augmented — and you will produce the vocabulary that players actually use with these scales.

On the piano, the whole tone scale falls under a fingering unlike any other, since the black and white keys alternate irregularly. Most pianists use 1-2-3-1-2-3 and accept that it feels wrong at first. It is worth persisting: this is one of the few scales where the awkwardness of the fingering matches the strangeness of the sound.

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