The hopscotch schema is IV–V–vi–I, and it is common in recent pop music (since 2010).A common variation is IV–I–V–vi (rotation). It can also be understood in its relative minor: i–VI–III–VII. The singer/songwriter schema is vi–IV–I–V or I–V–vi–IV, and it was common in 1990s singer/songwriter music.The doo-wop schema is I–vi–IV–V, and it was common in 1960s pop music.Each schema can have variations, such as chord substitution or rotation, while still remaining recognizable as that schema. I, IV, V, and vi are the most common harmonies in pop music, and they can be arranged into several schemas, each with a distinct sound.
