| Modes | I,II,III,IV,V,VI, VII |
|---|---|
| Component pitches | |
| C,D♭,E♭,F♭,G♭,A♭,B♭ | |
| Qualities | |
| Number ofpitch classes | 7 |
| Forte number | 7-34 |
| Complement | 5-34 |
Injazz, thealtered scale,altered dominant scale, orsuper-Locrian scale (Locrian♭4 scale) is aseven-notescale that is adominant scale where all non-essential tones have been altered. The triad formed from the root of the altered scale creates a diminished triad, but due to the inclusion of a diminished 11th, the scale comprises the three irreducibly essential tones that define adominant seventh chord, which are root, major third, and minor seventh and that all otherchord tones have been altered. These are:
The altered forms of some of the non-essential tones coincide (augmented eleventh with diminished fifth and augmented fifth with minor thirteenth) meaning those scale degrees areenharmonically identical and have multiple potential spellings. The natural forms of the non-essential tones are absent in the scale, thus it lacks a major ninth, a perfect eleventh, a perfect fifth, and a major thirteenth.
This is written below in musical notation with the essential chord tones coloured black and the non-essential altered chord tones coloured red.
The altered scale is made by the sequence:
The abbreviation "alt" (for "altered") used in chord symbols enhances readability by reducing the number of characters otherwise needed to define the chord and avoids the confusion of multiple equivalent complex names. For example, "C7alt" supplants "C7♯5♭9♯9♯11", "C7−5+5−9+9", "Caug7−9+9+11", etc.
This scale has existed for a long time as the 7th mode of theascending melodic minor scale.
The C altered scale is alsoenharmonically equivalent to the CLocrian mode with F changed to F♭. For this reason, the altered scale is sometimes called the Locrian♭ 4 scale.[1]
It is also enharmonically the seventhmode of theascending melodic minor scale. The altered scale is also known as the Pomeroy scale afterHerb Pomeroy,[2][3] the Ravel scale afterMaurice Ravel, and the diminished whole tone scale due to its resemblance to the lower part of thediminished scale and the upper part of thewhole tone scale.[4]
The super-Locrian scale (enharmonically identical to the altered scale) is obtained by flattening the fourth note of the diatonic Locrian mode. For example, flattening the fourth note of the C Locrian scale gives us the C altered scale:
The altered scale can also be achieved by raising the tonic of a major scale by a half step. For instance, raising the tonic of the C major scale by a half step (here spelled as an augmented unison) produces the scale C♯-D-E-F-G-A-B-C♯:
The altered scale can also be themajor scale with all of the notes except the tonic being flattened. For example, taking the C♯ major scale and flattening all of the notes except the tonic produces the C♯ altered scale (see above).
Because it contains the essential notes of a dominant seventh chord, it can be used to create melodies over the dominant chord in a jazz context. The added dissonance of the altered notes creates extra tension on the dominant.
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