TRINITY COLLEGE LONDON
USING ALTERED SCALES OVER DOMINANT CHORDS
Nik Preston takes us through three ways to exploit this useful theory
It’s that time again, theorists! This month’s column leads on from our previous investigation into various types of dominant scales and modes. Ready? The Altered Scale derives its name from the fact that it has the most ‘altered’ tensions of any seven-note scale in western harmony. It’s found on the seventh degree of melodic minor, the seventh mode.
If we identify chord tones and extensions in the usual way for tertiary harmony, we would find ourselves with a min7b5 chord. While this is theoretically correct, it has a more widespread application as a scale that we can employ over dominant chords because it contains a root, major 3rd and b7th. The ‘altered’ description gets its name from the fact that both a raised and flattened ninth are available, as well as a raised and flattened fifth. The flattened fifth, by the way, is just another way of notating the sound of a #11—in other words, they are enharmonic equivalents. So, in aC altered scale we have C, Db, D#, E, F#/Gb, G#, Bb—and you would most often use it over an altered dominant chord, sometimes written as either Calt or C7(#5#9).