Is it true that in a G major blues progression where the I chord, IV chord and V chord are all dominant 7 chords, you are actually playing in three different keys? With the G7 being the V chord of the key of C, the C7 being the V chord of the key of F, and the D7 being the V chord of the key of G? I've been playing guitar for almost twenty five years but am unfortunately pretty clueless when it comes to theory. Last night I was doing a bit of Google searching trying to understand why it is that in a G major blues progression the I chord (G7), IV chord (C7) and V chord (D7) are all dominant seventh chords. I was also wondering why a G minor pentatonic scale seems to fit well over all three chords. I came across a post on a site called Guitar Music Theory dot com which said the following: >Playing the minor pentatonic scale over a chord with a major third interval in it, is actually breaking the rules. As a result, some of the scale and chord tones clash.…