Mixolydian Mode

Mixolydian is a major scale with a flatted 7th. It's the dominant sound — the sound of a chord that needs to resolve but hasn't yet. Rock, blues, and country guitarists use it constantly, often without knowing it by name: any time you're playing a major scale but hitting that b7 note, you're in Mixolydian. It's also the modal foundation of most blues improvisation over dominant seventh chords.

Construction

The fifth mode of the major scale — starts on the 5th degree.
G Mixolydian = C major scale starting on G:
G A B C D E F G

Formula: 1  2  3  4  5  6  ♭7
Step pattern: W - W - H - W - W - H - W

Compared to the major scale (Ionian), Mixolydian lowers only the 7th degree. In G Mixolydian that's an F natural instead of F#. This one note changes the quality from major (which has a leading tone pulling toward the octave) to dominant (which hangs ambiguously).

Key Scales

G Mixolydian: G A B C D E F G
D Mixolydian: D E F# G A B C D
A Mixolydian: A B C# D E F# G A
E Mixolydian: E F# G# A B C# D E
C Mixolydian: C D E F G A B♭ C

Sound and Character

Major but grounded, earthy, with a bluesy edge. The flatted 7th prevents the resolution pull of the major scale — it doesn't have a leading tone — which gives Mixolydian a more relaxed, hanging quality. "Sweet Home Alabama" by Lynyrd Skynyrd is built on G Mixolydian. "Norwegian Wood" by the Beatles. "Hey Joe" by Jimi Hendrix. Virtually all blues-rock soloing over dominant seventh chords.

Mixolydian Over Dominant 7th Chords

G7 chord:    G B D F
G Mixolydian: G A B C D E F G

All four chord tones are in the scale.
The scale adds: A (9th), C (11th), E (13th) as available extensions.

This is why Mixolydian is the natural choice over dominant chords. It contains the major 3rd (defining major quality), the minor 7th (defining dominant quality), and a set of extensions that all sound good without alteration. For unaltered dominant chords — G7, A7, D7 — Mixolydian is usually the right starting point.

Where to Use It

Over V7 chords (dominant seventh) in a major key. Also over static dominant seventh chords — power chords in rock, vamps in blues and funk. In a 12-bar blues in A, Mixolydian (or the blues scale, which is related) over A7, D7, and E7 covers most of what you need. The I chord in a blues is actually a dominant seventh chord (A7, not Amaj7), so Mixolydian works over the I too — not just the V.