Is G mixolydian just C major?

Same seven notes, different centre. What makes it mixolydian is that G is the reference point, so F sounds like a b7 rather than the 4th degree of C. On the fretboard the shapes are identical; in your ear they are not.

When should I use the altered scale over G7?

When the G7 resolves - typically down a fifth to C. The altered scale is pure tension and needs a resolution to make sense. Over a static dominant vamp it usually sounds wrong rather than sophisticated.

Can I play the C major scale over G7?

Yes - it contains every chord tone. Just be aware that C itself is the 11th and sits a half step above the chord's 3rd, so it is a passing note rather than a place to land.

Which scale works over G7?

There is no single answer, and that is the useful part. A G7 chord can take at least five different scales, and which one is right depends entirely on what the chord is doing - resolving to C, sitting still in a blues, or being pushed as far as it will go.

G7 | Cmaj7

Chord tones

G7G – B – D – F1 – 3 – 5 – b7
Cmaj7C – E – G – B1 – 3 – 5 – 7

Open in the improviser →

Connections: G7 → Cmaj7

G → Gcommon tone
B → Chalf step up
F → Ehalf step down
D → Ewhole step up

Common tones: G, B

Scale notes

G Mixolydian over G7

G – A – B – C – D – E – F

1 – 2 – 3 – 4 – 5 – 6 – b7

MixolydianMatches all four chord tones of a dominant 7
Blues ScaleThe core blues sound: the b3 works as a blue note against the chord's major third
Dominant BebopAdds the passing tone for even eighth-note lines

Why this works

Start with what the chord actually contains: G–B–D–F. Any scale that fits must contain those four notes; everything else is a choice. G mixolydian (G A B C D E F) is the default - it is C major started from G, so it fits a G7 that resolves to Cmaj7 and adds no tension of its own. The G blues scale ignores the theory and works anyway, because the b3 (Bb) rubbing against the chord's B natural is the sound of the blues rather than a mistake. Dominant bebop is mixolydian with an added major 7th, a passing note that makes eighth-note lines land the chord tones on the beats. The altered scale is what you use when the G7 is going somewhere hard: it keeps B and F and alters everything else, giving b9, #9, b5 and #5 at once. Half-whole diminished sits between the two - it gives you b9 and #9 but keeps a natural 13. The practical rule: use mixolydian when the dominant is functioning normally, reach for altered or diminished when you want the resolution to feel earned, and use the blues scale when the harmony is static.

How to practice this

Play the same phrase with different scales over the same chord and listen to what changes.

Step by step

Loop G7 – Cmaj7 at 80 BPM and set the scale to G mixolydian. Improvise for one chorus.
Switch to the blues scale without changing anything else. Notice that the b3 now clashes and that it sounds intentional.
Switch to altered and play only over the G7 bar, resolving into Cmaj7 on the change. It will only work if you resolve.
Go back to mixolydian and find the one note it contains that the altered scale does not: C, the 11th - the note most players avoid over a dominant.
Pick the scale that fits the song you are actually playing, and stay with it for a week.

Practice this with real lessons

You are looking at the half-step resolutions between G7 and Cmaj7. These lessons work on exactly this kind of movement.

No lesson covers this exact context yet.

No lesson matches this exact context yet.

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Frequently asked questions

Is G mixolydian just C major?: Same seven notes, different centre. What makes it mixolydian is that G is the reference point, so F sounds like a b7 rather than the 4th degree of C. On the fretboard the shapes are identical; in your ear they are not.
When should I use the altered scale over G7?: When the G7 resolves - typically down a fifth to C. The altered scale is pure tension and needs a resolution to make sense. Over a static dominant vamp it usually sounds wrong rather than sophisticated.
Can I play the C major scale over G7?: Yes - it contains every chord tone. Just be aware that C itself is the 11th and sits a half step above the chord's 3rd, so it is a passing note rather than a place to land.