Watch the Inhale online guitar lesson by Jeff McErlain from Beginner Blues-Rock Soloing
I'm sure I don't have to tell you that this groove is basically Pink Floyd's "Breathe". The chord progression is very simple, Em to A7. The scale we're primarily going to use is Em pentatonic, although the full scale that we'd use over this progression is E Dorian. The notes of E Dorian are E F# G A B C# D E, but don't let that name scare you. E Dorian contains an E minor pentatonic scale, the notes of which are E G A B D, so as you can see all we're missing is the C# and F#. These notes are often the ones that you may play by accident and realize that they sound pretty good.