This post is part of a series about the modes.
To hear a Mixolydian mode, play the white keys on a piano from G to G. To start this mode on another note, play a major scale with a lowered 7th step. For example; G major has one sharp, F. Since F sharp is the 7th step of the G major scale, we play F natural to hear a mixolydian scale.
Mixolydian pops up in folk and Troubadour music a lot. So often, it doesn't even always get labeled. I know a number of performers who prefer the lowered 7th sound so much that they have trouble playing in a major key. They just can't help tossing in a lowered 7th here and there. And interestingly, the lowered 7th is used in Jazz quite frequently too. This scale seems to be one of the areas where folk, Jazz and Classical music meet with relative ease.
One tune in Mixolydian that I play is called "The Little Beggerman" or "The Red Haired Boy" (same tune, just different names for the vocal or instrumental versions.) It is very upbeat and fast (especially the way I play it) but it is missing the wide open shine of major tunes. Instead, it has a tongue in cheek quality to the melody that comes partly from the lowered 7th.
This mode is also great for laments, lullabies or songs about longing. I love the sense for reaching out but not quite touching I can get from this scale. The lowered 7th can also make it easier to spin out melodies (fast or slow) since it doesn't pull to the tonic the same way the 7th note in the major scale does.
I especially like the way Mixolydian can switch back and forth from slow and thoughtful to fast and flashy. It is an easy going scale that adapts to changeable moods within a single song which is a great way to keep an audience involved in a performance.