The I–V–vi–IV progression is a common chord progression popular across several genres of music. It involves the I, V, vi, and IV chords of any particular musical scale. For example, in the key of C major, this progression would be: C–G–Am–F. Rotations include:
I–V–vi–IV : C–G–Am–F (optimistic)
V–vi–IV–I : G–Am–F–C
vi–IV–I–V : Am–F–C–G (pessimistic)
IV–I–V–vi : F–C–G–AmThe '50s progression uses the same chords but in a different order (I–vi–IV–V), no matter the starting point.