The next thing we’re gonna do is to utilize this interval over a static chord, in this case A7 (consisting of root-3rd, 5th, b7). The scale for the chord would be A mixolydian (notes of the D major scale against an A7 chord). Here’s the interval structure: 1-2-3-4-5-6-b7.
Our task will be to play a sixth from every note of the scale. That means we play: 1 to 6; 2 to 7; 3 to 8, etc. Depending on where we are within scale we’ll either get a major or minor sixth.
Now if this is all too confusing for you, don’t worry. You can expand your vocabulary by just getting this exercise under your fingers.