I–IV–V–I

In music, I–IV–V–I or IV–V–I is a chord progression and cadence that, "unequivocally defines the point of origin and the total system, the key." Composers often begin pieces with this progression as an exposition of the tonality:
According to theorist Oswald Jonas, "long with motion toward the fifth, IV appears as a corrective, depriving V of its independence and pointing it back in the direction of its origin ." In the key of C, IV provides the note F and eliminates the possibility of G major, which requires F. The progression is also often used at the end of works and sections.
A popular variant is vi–IV–V–I, commonly known as the "Komuro progression", namesake of Tetsuya Komuro who popularised the progression.