Much adieu is made about the blues and pentatonic scales for creating cool blues riffs. But here’s another scale that’s useful for making riffs: the Mixolydian scale. Before we talk about this scale, let’s use it. Play the following exercise. The numbers at the bottom of each staff tell you which fingers to use.
We’ve actually used three different Mixolydian scales here: the A Mixolydian, the D Mixolydian, and the E Mixolydian. Notice how the notes in each Mixolydian scale contain the arpeggios, or chord tones, for chords in the A blues. For example, the first measure would be an A7, if you were playing chords.
So, the arpeggio notes for A7 are A, C#, E, and G. Now look at the notes in the Mixolydian scale for that measure: A, B, C#, D, E, F#, and G. All the arpeggio notes are here on the strong beats, which are beats one and four. The non-chord tones are on the weak beats. These non-chord tones or notes are called passing tones.
Noticing whether a note falls on the strong or the weak beats is important, because it deeply affects the music.
When you make riffs with the A Mixolydian scale, you want to make sure the strong beats tend to use the notes A, C#, E, and G — the tones of the A7 chord. If the passing tones from the A Mixolydian scale fall on the strong beats, your playing won’t sound like the blues.
Where Does the Mixolydian Scale Come from?
Once you recognize that the A Mixolydian scale is really just an A7 arpeggio with some passing tones installed between the chord tones, you can rephrase your question to this: what scale do I find the A7 chord in? Answer: the D major scale. Compare the D major scale to the A Mixolydian scale:
Notes in D major: D, E, F#, G, A, B, C#
Notes in A Mixolydian: A, B, C#, D, E, F#, G
Notice that the notes in each of these groups are the same. The difference is that each group starts and ends on a different note.
A Mixolydian scale has the same notes as a major scale. The only difference is you’re starting from the fifth degree of the scale instead of the first.
The Mixolydian scale is an example of a mode. Note how close this term is to the term “mood.” That’s not a coincidence: Different modes produce different moods. The Mixolydian mode is a good way for inducing a bluesey kind of mood, which you saw and heard in this exercise.
Other Places to use Mixolydian
You don’t have to be restricted to using the Mixolydian just for blues playing. You can generally use a Mixolydian scale any place where you can use the dominant 7th chord that’s based on the Mixolydian.
For example, let’s say you’re playing this mini-progression: A, G, and D. All of these chords are in the key of D major. What dominant 7th chord goes with the key of D major? Yes, A7. So you can play an A Mixolydian scale on top of this progression.
If you’re instead working with the chords E, D, and A, which are all in the key of A major, you can use notes from the E7 chord, or E Mixolydian, for playing over the changes. You can do this because E7 is the dominant 7 chord in A major, and E Mixolydian is the mode or scale that emphasizes the E7 chord tones.