I'm trying to do harmonic analysis of "Walk this Way" by Aerosmith. Verses and choruses uses I to IV progression, but I wonder about the riff in the bridge. It seem to be played in the E key. Joe Perry, the guitarist and composer, said:
"I didn't want the song to have a typical, boring 1, 4, 5 chord progression. After playing the first riff in the key of C, I shifted to E before returning to C for the verse and chorus."
I think that the E key is the V of the relative minor scale (A minor) of the C major key, in which the song is written. But it is a rather uncommon way to modulate between the keys (it should modulate to the E key through dominant seventh B chord, in means of classical harmony).
Can anyone please tell me what kind of modulation is this? Or, if my analysis is incorrect, can anyone please tell me what is the harmonic reason to play the bridge in E scale?
Thank you all for your help! It gave me a deeper insight into harmony of popular music.