5-1 - Cadence

The 1-5 asks a question. The 5-1 answers it. Great songwriters use the tension between the two to create narrative arcs.

The magic of the V-I progression is largely driven by the "leading tone." In a major key, the leading tone is the seventh note of the scale. In the key of C Major, this note is B. 5-1 cadence

Inside every dominant 7th chord (the standard "5" chord in jazz) lives a specific interval called the (three whole steps). In a G7 chord (G - B - D - F), the tritone exists between the 3rd (B) and the 7th (F). The 1-5 asks a question