Harmonic Patterns In Songs

When I learn other people's music I sometimes notice patterns in the harmony that I want to remember and learn from. I will try to document them here.

Changing the home chord for the chorus

In folk and country tunes there is often a focus of just a few primary chords, often I, IV and V. Songs will often make a loop of these primary chords. For the verse sections of the song one of these chords will be chosen as the starting chord. For the chorus one of the other primary chords is chosen as the starting chord. This provides some sense of journey and motion with very little new material. The two sections often end with the same or similar harmonic idea but begin with a different structure. I am curious how this idea can be extended into other kinds of modal writing where there are analogous primary chords to Ionian's I, IV, and V chords.

examples:

Sweet Revenge - John Prine

Its [[Verse Chorus Form]]. The verse starts on I and the chorus starts on IV

verse: I - IV - I - V7 - I - IV - I - V7 - IV - I chorus: IV - I - I - V7 - I - IV - I - V7 - IV - I

Christmas in Prison - John Prine

Its [[Verse Chorus Form]]. The verse starts on I and the chorus starts on V

verse: I - IV - I - V - I - IV - I - V - I chorus: V - IV - I - IV - I - V - I - IV - I - V - I