Mixolydian

The notes

D E F♯ G A B C, then D. It is the fifth mode of G major and shares its single sharp. Playing G major from D is the quickest route to it.

The C natural turns the tonic chord into D7 without implying that the music is going anywhere. That is the defining quality: a dominant seventh that functions as home.

On the fretboard

Open position covers the scale using the open D, G, B and E strings. The tenth-fret position with the root on the low E gives the movable form.

Because both D and G major shapes belong to the mode, a riff can alternate between them indefinitely and stay inside it — which describes a large amount of folk-rock writing.

Where it is used

Irish and English traditional music, where tunes in D with a C natural are mixolydian by construction. Rock uses the same scale over a static D7 or a D–C–G progression.

In jazz it is the scale over the V chord, and D mixolydian is what fits D7 in the key of G — the most common dominant on the instrument.

The mode also explains a large family of riffs: any figure that alternates D and C major chords without ever reaching G is mixolydian, and the ear reads it as rock rather than as folk purely because of the tempo.