Stop 5 of 6
Symmetric and altered scales
Diminished, whole-tone and the altered scale.
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Stop 5 of 6
Diminished, whole-tone and the altered scale.
The major scale and its modes are asymmetric: their whole and half steps are spread unevenly, which is why every note has a different role. In this stop you'll explore scales that work like a kaleidoscope: they repeat the same pattern over and over. That symmetry makes them strange, brilliant and very useful over altered dominants. You'll also meet the , modern jazz's favourite tool for the 7alt chord.
Listen to three scales starting on G. The first is Mixolydian, which you already know. The other two are :
The diminished scale alternates half and whole steps without a break. The whole-tone scale uses only whole steps. Draw them on the circle of twelve notes and perfectly regular shapes appear:
Start on the root of a dominant with a half step and alternate: H W H W H W H W. On G you get:
Now read it as chord degrees: 1, ♭9, ♯9, 3, ♯11, 5, 13, ♭7. It contains every note of G7 plus three altered tensions and one natural one (the 13). That's why it's the perfect for G7♭9 and G13♭9, as long as the chord has a perfect fifth or a natural 13.
String 6, Fret 3: G2 · 1 · Root
This line runs down the scale and resolves to C: the final B rises a half step to C.
And now the magic of symmetry: since the scale repeats every minor third, the same line moved 3 frets is still inside it. What's more, G7♭9, B♭7♭9, D♭7♭9 and E7♭9 share exactly the same diminished scale.
The G diminished scale holds four major triads whose roots are a minor third apart: G, B♭, D♭ and E (with G♯ written as A♭ in the scale). It's a very musical way to use the scale: instead of running through it note by note, arpeggiate those triads over G7♭9. Each one highlights different tensions:
| Triad over G7 | Notes | Degrees over G | Sound |
|---|---|---|---|
| E | E G# B | 13, b9, 3 | G13♭9, much used in jazz |
| D♭ | Db F Ab | #11, b7, b9 | the tritone substitute |
| B♭ | Bb D F | #9, 5, b7 | bluesy flavour |
| G | G B D | 1, 3, 5 | the chord itself |
This trick is sometimes called an upper structure: a simple triad played over a dominant's shell produces a chord with complex tensions. The triads can be played in any inversion, so you can find them close to whatever position you're in.
If you start with a whole step (W H W H…), you get the whole-half version, the one that fits diminished seventh chords. On Bdim7:
Compare its notes with the G diminished scale from before: B C# D E F G Ab Bb. They're the same. It makes sense: Bdim7 is G7♭9 without its root, as you saw with passing diminished chords. And since a dim7 chord is also symmetric (four notes a minor third apart), its shape on the neck repeats every 3 frets:
String 6, Fret 1: F2 · ♭5 · Fifth
The has no half steps and no perfect fifths. Without the perfect fifth nothing feels solid: it's the sound of a dream, of a cloud. On G: 1, 9, 3, ♯11, ♯5, ♭7. It fits G7♯5 and G9♯5, dominants with an augmented fifth and a natural ninth.
Practise it with two notes per string: the pattern is so regular that once you've memorised it on one string, you have it on all of them.
What if the chord asks for all the alterations at once: b9, #9, #11 and b13? The answer is the altered scale: 1, ♭9, ♯9, 3, ♯11, ♭13, ♭7. It keeps the essentials of the dominant (root, third and seventh) and alters everything else.
The trick to finding it: it's the seventh mode of melodic minor. G altered has the notes of A♭ melodic minor (Ab Bb Cb Db Eb F G), starting from G. In practice: over a 7alt chord, play the melodic minor a half step above the root.
String 6, Fret 3: G2 · 1 · Root
G altered (G Ab Bb Cb Db Eb F) and D♭ Lydian dominant (Db Eb F G Ab Bb Cb) have the same seven notes. That's why playing the altered scale over G7 sounds like "implying" D♭7, its tritone substitute. Both are modes of A♭ melodic minor: the altered scale is the seventh mode and Lydian dominant the fourth.
Notice the spelling too: G's third appears as C♭ (the fourth degree of A♭ melodic minor), but over the chord you hear it as B, the major third. And the ♯9 is often written B♭. Scale theory uses the parent scale's spelling; chord analysis uses the degrees'.
Read the tensions in the chord symbol (or hear them in the accompanist's voicing) and pick the scale that contains them:
| Chord | Tensions | Scale |
|---|---|---|
| G7, G13 | 9, 13 | Mixolydian |
| G7♯11 | 9, #11, 13 | dominant |
| G7♭9 towards minor | b9, b13 | Phrygian dominant |
| G7♭9 with 13 | b9, #9, #11, 13 | half-whole diminished |
| G7♯5 | 9, #11, #5 | whole-tone |
| G7alt | b9, #9, #11, b13 | altered |
| Bdim7 | — | whole-half diminished |
Goal: Play the diminished line in four positions (frets 3, 6, 9 and 12) over G7b9 → C, always resolving to a note of C.
Goal: Improvise eight bars over Dm7 – G7alt – Cmaj7, changing scale on every chord and resolving the b9 or b13 of G7alt.
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