Watch the Mixolydian Scale online guitar lesson by Stu Hamm from Stu Hamm U: Bass Basics
Here is the 3rd scale that you really need to learn, the Mixolydian scale. It is a Major scale (with a Major 3rd) but with a flatted seventh tone. This scale is where the Dominant 7th chord comes from, and is used extensively in blues, rock and pop music. Just running the Arpeggio of a Mixolydian scale will yield countless bass lines that will be familiar to you, so this is one that you are going to use all the time. We’ll do a series of exercises to get you used to fingerings and once again emphasize that using the same fingering patterns you can play the same thing on different positions on the neck. Make sure to practice slowly and concentrate not only on the notes, but on the SOUND of the notes as well.