Chord progression basics
Apps like Tin Pan Rhythm start from a chord progression. Two patterns cover a lot of ground.
I–IV–V–I
The I–IV–V–I progression is a foundational cadence: it establishes the key. Composers often open pieces with it and it is common at the ends of works and sections.1
| Degree | I | IV | V | I |
|---|---|---|---|---|
| In C major | C | F | G | C |
The IV chord brings in F natural, which rules out G major (that key needs F sharp), so the ear settles on C.1
The 12-bar blues
The 12-bar blues uses the same three chords over twelve bars.2
| Bars | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| 1–4 | C | C | C | C |
| 5–8 | F | F | C | C |
| 9–12 | G | F | C | G |
Jazz players stretched the form: Charlie Parker's "Now's the Time" and "Billie's Bounce" and Sonny Rollins's "Tenor Madness" are 12-bar blues, and John Coltrane's "Equinox" and "Mr. P.C." are minor-key versions.2
Try it
You can loop either pattern in any iPad music app, see iPad music apps.