Debussy -- "Voiles"

The discussion about the division of the octave into major thirds in Coltrane's "Giant Steps" got me thinking about other instances of this technique. There are four possible ways of dividing the octave symmetrically: two tritones, three major thirds, four minor thirds and six whole tones. "And a partridge in a pear tree" Right season, wrong song!

The great benefit of dividing the octave in these ways is to avoid traditional harmony, which seems to have been Coltrane's intention. I'm still thinking about that. But let's have a look at how someone else approached this. I'm thinking of "Voiles" from the Preludes, Bk 1 of Claude Debussy. Here is the piece:

It is so handy to have the score right there. As we can see right from the opening, Debussy is using the whole-tone scale:

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Here is the opening idea; whole tones in thirds descending from #III to bVI, then via an octave displacement to bV:

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Whole tone scales always look a bit odd because our notation is not designed for them. How you spell a note is pretty much arbitrary: F# and Gb are just the same in a whole tone scale. Soon after this opening Debussy introduces two other ideas. The three ideas then co-exist, on different layers:

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The top layer is the opening idea in thirds, but moved to the beginning of the measure. The second idea is the Bb bass note pedal which was introduced in measure 5 and the third idea is the rising augmented chords, originally presented in octaves only in measure 7. The example above is how they look together. The only triads possible in a whole tone scale are augmented ones. Now, what about that Bb pedal? Well, it is a whole tone away from the 'tonic', C. In the contrasting middle section of the piece the pedal stays on Bb and the key signature moves to five flats (Bb minor?). Debussy 'cadences' in the last three measures by finally dropping the Bb pedal which has been present throughout the piece, and by reiterating the movement D/F# to C/E several times, ending on C/E. This is somewhat analogous to the traditional technique of zoning in on the dominant by using an augmented sixth chord with the notes a semi-tone above and below the dominant. Here he zones in on C by stressing the notes a whole tone below--the Bb--and above--the D.

Successful piece, I think. It shows that you can structure a piece using a whole tone scale. The melody comes from whole tones (though in that middle section he uses the pentatonic scale as well), the harmonies come from the same scale and he creates a kind of 'modal' cadence at the end. But Debussy just did this once in a short piece and I think that we can conclude that the whole tone scale, by itself, is very limiting.

Now the octatonic, on the other hand... But that's a story for another day.