The 2-5-1 (or ii – V – I) chord progression is the most used building block in jazz music. It’s basic version consists of the ii minor seventh chord, followed by a V dominant seventh chord and the I major seventh chord. These seventh chords are taken from the diatonic chords for the respective key. So if you are in the key of F major, for example, the diatonic chords are the following:
The diatonic seventh chords in the key of F major
If you create the 2-5-1 progression from these seventh chords, it looks like this, with the sevenths marked in blue:
G minor 7
C dominant 7 or just C7
F major 7
A better way to voice the chords is to play an inversion for the C7 chord:
C7 inverted
Because this chord progression appears so often in jazz music, it is good to know it in all twelve keys. Make sure to practice it if you want to play jazz piano. Knowing your 2-5-1s in and out helps you to play countless tunes and solo over them.