Four chords guitar

I–V–♭VII–IV may be viewed as a variation of I–V–vi–IV, replacing the submediant with the subtonic. It consists of two I-V chord progressions, the second a whole step lower (A–E–G–D = I–V in A and I–V in G), giving it harmonic drive. There are few keys in which one may play the progression with open chords on the guitar, so it is often portrayed with barre chords (“Lay Lady Lay”). The use of the flattened seventh may lend this progression a bluesy feel or sound, and the whole tone descent may be reminiscent of the ninth and tenth chords of the twelve bar blues (V-IV). The progression also makes possible a chromatic descent over a contiguous heptachord (minor third): 8^{displaystyle {hat {8}}}–♯7^{displaystyle {hat {7}}}–♮7^{displaystyle {hat {7}}}–6^{displaystyle {hat {6}}}. The roots of the chords are in Mixolydian, which is used in “Lay Lady Lay”, though the progression contains one note outside of Mixolydian (the third of V, see Phrygian dominant scale) and other modes, such as major, may be used when performing the progression.