Respuesta :

In a musical composition, a chord progression or harmonic progression (informally chord changes, used as a plural) is a succession of chords. ... For example, the previously mentioned chord progression, in the key of C major, would be written as C major–A minor–D minor–G major in a fake book or lead sheet.

The capital letters are major chords, lowercase letters are minor, and the last one is diminished. So, when you talk about chord progressions, the common way to write them is I – IV – V. This means that all three chords will be major ones, and in the scale of C major, the progression is C – F – G.