This post is for my students at the City of Bath College.
The Mixolydian mode is the fifth mode of the Major Scale. In the key of A the Mixolydian Mode consists of the following seven notes: A, B, C#, D, E, F# G (R, 2, 3, 4, 5, 6 b7).
Use this generic code to spell the scale in any key: 2 2 1 2 2 1 2 or T T S T T S T
Position 1 (Mixolydian Mode)
Start this shape with your second finger.
Position 1 (Three Note Per String)
Start this three notes per string shape with your first finger.
For further reading about the history of the mode see Wikipedia: Mixolydian Mode