I'm having a difficult time understanding what scales match with what chords. To my understanding you can use whatever scales have the same notes as the key you're in but in a song by SRV (key of E) he uses the e minor pentatonic scale, E blues scale, E mixolydian, A mixolydian, and B mixolydian. For the most part all the notes match up to the notes in the key of E major but there are some differences. Such as some of the scales using a G and others using a G#. Or a Bb instead of B. Wouldnt this be a problem? The chords used are B7,A7,E7, and C7. Also, would I need to switch scales with ever chord change? Like with the E mixolydian scale under the E7 and then changing to the B mixolydian scale under the B7? Or could I just stay in the E7 or maybe even the E minor pentatonic scale the whole song if I wanted to? Any response would be much appreciated. This stuff I really confusing. If someone could also provide a response for how to know what scales you can play under what chords that would also be much appreciated