Jazz Guitar Scale Finder

Scales for a ii-V-I

The progression everything else is measured against. In C major the three obvious answers are D Dorian, G Mixolydian and C Ionian — and all three are the same seven notes, the C major scale, read from three different places. That is the point: at speed you are not changing scale, you are changing which note you treat as home.

And when the dominant wants to pull harder

Tell the tool the G7 is resolving and the answer changes. The altered scale and the half-whole diminished scale both supply the b9 and #9 that a plain mixolydian cannot, and both make the arrival at Cmaj7 sound more inevitable — because they contain more notes that are a semitone away from where they are going.

Scales for major chords

Ionian is the default and Lydian is the alternative, and the difference between them is one note: the fourth. Over a maj7 the natural fourth sits a semitone above the third, so it clashes if you stop on it — which is exactly why so many players prefer the raised fourth of Lydian, where nothing is a semitone above anything. If the chord symbol says #11, Lydian stops being an alternative and becomes the answer.

Scales for dominant chords

This is where the choices multiply, because a dominant is the one chord that is allowed to carry almost any tension. The question that decides it is not which notes are in the chord — it is whether the chord is going somewhere. A dominant that resolves can take the altered scale, the half-whole diminished scale or phrygian dominant, all of which are full of notes a semitone away from the target. A dominant that is not going anywhere — a blues, a modal vamp — takes mixolydian, lydian dominant, or a pentatonic laid across it, because there is nothing for tension to resolve to.

How chord tones and tensions decide the scale

A chord scale is not a list of notes that sound nice. It is the chord, plus the notes that fill the gaps between the chord tones. Every scale in this tool is checked against that: it must contain the notes the chord’s identity depends on, and it is marked down for every note that sits a semitone above a chord tone without being a legitimate tension. That single rule is what separates Ionian from Lydian over maj7#11, and Dorian from Aeolian over a m7 — nothing about it is hard-coded, it falls out of the arithmetic.

Which is also why the tool refuses some pairings outright. An altered dominant has no natural fifth, no 13 and no 11 — that is what the word "altered" means — so mixolydian is not offered for a 7alt at all, however many websites list it.

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