The Mixolydian mode is a medieval mode starting on the fifth degree of the diatonic scale with half steps between the third and fourth and sixth and seventh degrees. The Mixolydian mode is a major scale only one note different — a flatted seventh — from the major scale that begins on the same note. For example, G Mixolydian, which starts on G of the C major scale, is:
G A B C D E F G
whereas G major is:
G A B C D E F♯ G
Being a dominant seventh scale, the Mixolydian is a perfect fit for the chord of the same name (see seventh chord). It's a scale that turns up quite often in jazz, fusion, and funk, and it can be thought of as another starting point for playing the blues, too. It has the same kind of unresolved sound that the dominant chord has and therefore fits anything that's remotely blues-based.