The II-V-I is a harmonic progression typical of Jazz music (but not only of course, also in Rock, Blues and even Classical), which creates a path of tension and resolution. It refers to three chords arranged in sequence: the II, V and I degree (subdominant, dominant and tonic) a specific key. In a II-V-I progression, these three chords are played in sequence, thus tension builds as one moves from the II degree chord to the V degree chord, as the V degree creates a strong expectation of resolution towards the I degree . The first degree chord then satisfies this expectation, creating a feeling of closure. In the context of jazz guitar, this progression is often used to create improvisations and develop sophisticated melodic lines. Today, however, we are dealing with chords and harmonic substitution, i.e. how to replace pre-existing chords, obviously maintaining all of the above.
