Altered scale
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In jazz, the altered scale is a seven-note scale that differs from the locrian mode in having a lowered fourth scale degree. Starting on C, it contains the notes: C, D♭, E♭, F♭, G♭, A♭ and B♭. (This is the C locrian mode, C-D♭-E♭-F-G♭-A♭-B♭, with F changed to F♭. For this reason, the altered scale is sometimes called the "super locrian mode.") It is the seventh mode of the melodic minor ascending scale. The scale is sometimes spelled with two thirds rather than a flatted fourth scale degree--e.g. C-D♭-E♭-E-G♭-A♭-B♭, with E substituting for F♭. In contrast to the term acoustic scale, the term "altered scale" almost always refers to this particular mode of the melodic minor, rather than the scale itself. In this sense, the term "altered mode" would be more accurate.
The altered scale appears sporadically in the works of Debussy and Ravel (Tymoczko 1997), as well as in the works of recent composers such as Steve Reich (see, in particular, the Desert Music). It plays a fundamental role in jazz, where it is used to accompany altered dominant seventh chords starting on the first scale degree. (That is, the scale C-D♭-E♭-E-G♭-A♭-B♭ is used to accompany chords such as C-E-G♭-B♭, the "dominant seventh flat five" chord.
The C super locrian scale consists of the notes
C D♭ E♭ F♭ G♭ A♭ B♭ C
One way to obtain the altered scale is by raising the tonic of a major scale by a half step; for example, when we raise the tonic of the B major scale, which has the notes
B C♯ D♯ E F♯ G♯ A♯ B
we get the C altered scale
C C♯ D♯ E F♯ G♯ A♯ C
the notes of which are enharmonic (identical, in the equal temperament system) with the notes of the C altered scale as it was first described on this page.
Like the other modes of the melodic minor ascending, the altered scale shares six of its seven notes with an octatonic (or "diminished") scale, and five of the six notes of a whole tone scale, and thus is occasionally referred to as the "diminished whole tone scale." (For example, the altered scale C-D♭-E♭-E-G♭-A♭-B♭ shares all but its A♭ with the octatonic scale C-D♭-E♭-E-F♯-G-A-B♭; while sharing five of the six notes in the whole-tone scale C-D-E-G♭-A♭-B♭.) This accounts for some of its popularity in both the classical and jazz traditions (Callender 1998, Tymoczko 2004).
[edit] Sources
- Callender, Clifton. 1998. "Voice-leading parsimony in the music of Alexander Scriabin." Journal of Music Theory 42, no. 2 ("Neo-Riemannian Theory", Autumn): 219–33.
- Tymoczko, Dmitri. 1997. “The Consecutive-Semitone Constraint on Scalar Structure: A Link Between Impressionism and Jazz.” Integral 11:135–79.
- Tymoczko, Dmitri. 2004. “Scale Networks in Debussy.” Journal of Music Theory 48, no. 2 (Autumn): 215–92.
[edit] External links
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