Formula
- Degrees: 1 b2 b3 b4 b5 b6 b7 (as a mode) = in jazz reading 1 b9 #9 3 b5 b13 b7.
- Steps: H W H W W W W (1 2 1 2 2 2 2 semitones).
- Parent scale: 7th mode of melodic minor. B altered = notes of C melodic minor from B: B C D Eb F G A.
- On G (the most used case, G7alt → C): G Ab A# B Db Eb F in jazz spelling (in modal letter spelling: G Ab Bb Cb Db Eb F), from Ab melodic minor (G# melodic minor: G# A# B C# D# E# F##).
Names: Super Locrian, altered scale, diminished whole-tone: the first half recalls the diminished scale (1 b9 #9 3), the second the whole-tone scale (3 b5 b13 b7).
Characteristic note and color
It contains all the alterations of the dominant: b9, #9, b5 (#11), #5 (b13), together with the guide tones 3 and b7. It has neither the perfect 5th, nor the natural 9th, nor the natural 13th. Color: maximum dominant tension, “outside” but controlled; all the tensions want to resolve by semitone to the tonic.
Why it works
The “foreign” notes of the altered dominant are almost all a semitone away from a note of the target tonic. G7alt → Cmaj7 or Cm:
- Ab (b9) → G; Db (b5) → C; Eb (b13) → D or E; A# / Bb (#9) → A or B.
It is the same principle as tritone substitution: Db7 contains Db F Ab Cb, i.e. the b5, b7, b9 and 3 of G; the altered scale of G coincides with Db Lydian dominant (Db Eb F G Ab Bb Cb).
Chords that can be derived
- G7alt = G B F + any combination of Ab, A#, Db, Eb.
- Typical voicings: G7#9b13 (G B F A# Eb), G7b9b13 (G B F Ab Eb), G7#9b5 (G B F A# Db).
- Upper structures: the Eb major triad (Eb G Bb) over the tritone B–F produces G7#9b13; the Db major triad (Db F Ab) over G–B produces G7b9b5; the Ab minor triad (Ab Cb Eb) over G produces G7b9b13 without the 5th.
- The related modes (same melodic minor of Ab): Abm(maj7), Bbm7, Cbmaj7#5, Db7#11, Eb7(b13), Fø7.
Where it is used
- V7 that resolves to a tonic, especially a minor one (G7alt → Cm): the classic use of bebop and hard bop.
- Resolved secondary dominants (A7alt → Dm7 in the I – VI7alt – ii – V turnaround).
- Last chord before the return in a jazz head, for maximum push.
- In modern film music and fusion, as a tense color (often as a held “alt” chord).
Examples in context
- “Autumn Leaves”: D7alt → Gm (V7 of the relative minor).
- “Blue Bossa” (Kenny Dorham): G7alt → Cm7.
- In the solos of Charlie Parker, Wes Montgomery and Michael Brecker, altered lines over the V are a stylistic trait; the reference manual is Levine, The Jazz Theory Book (chapter “Melodic Minor Harmony”).
Common mistakes
- Using it over a V7 that does not resolve (bVII7, IV7 of the blues): there you need Lydian dominant or Mixolydian.
- Mixing the perfect 5th and the b5/#5 in the same voicing.
- Having the bass play the altered tensions: the bass holds G (or the substitute Db).
- Using it over a chord with the natural 13th indicated in the melody (G13): it clashes.
Exercise
- ii–V–i in C minor: Dø7 – G7alt – Cm(maj7); play the Eb triad over G7alt and then the Ab melodic minor scale starting from G.
- Write three different voicings of G7alt for pad and compare them with the same melody.
- Think “a semitone above”: the altered scale of G is the melodic minor of Ab. Practice in 12 keys with this rule.
Connections
Melodic minor and its modes; Altered chords; Upper structure triads; Tritone substitution; Diminished scale; Super Locrian bb7.