The Mixolydian is a mode I associate with country, blues, heavy rock and the Beatles. It isn’t the only scale used in those styles, and it isn’t limited to those styles, but with it’s dominant seventh tonic chord and the emphasis on the seventh note of the scale, it always conjures up images of old fashioned, American rock. It’s a beer drinking, gibson chugging, guitar twangin’ mode (or at least, that’s how it feel to me).
The mixolydian mode is almost the same as the ‘normal’ major scale, except that the seventh note is flattened by one semitone. So in C Mixolydian the notes would be C D E F G A Bb C.
You can do the same to any major scale. For example, G mixolydian is G A B C D E F G (all the white notes on the keyboard starting at G). D mixolydian is D E F# G A B C D.
To generalise, the intervals in the mixolydian mode are:
Tone Tone Semitone Tone Tone Semitone, Tone
It might look like a tiny change but having that flattened seventh creates a very distinct harmony that is miles away from the major scale.
The seven chords in those mode are:
I7 iimin7 iii Half-dim IV Maj7 v Min7 vi Min7 VII Maj7
In C Mixolydian: C7 Dmin7 E Half-dim F Maj7 G Min7 A Min7 Bb Maj7
In G Mixolydian: G7 Amin7 B Half-dim C Maj7 D Min7 E Min7 F Maj7
In the major scale, we’re used to chords VI and V being important. Chord V in particular often comes before I to form a cadence. In the Mixolydian mode, the VII chord performs a similar function, as in one of the most famous songs that uses the mixolydian mode, Sweet home Alabama:
What to do if you want that mixolydian sound? Try writing chord progressions that use chords I and VII, eg. C Bb F, G C F and work from there.