COMPLETE LESSONS AVAILABLE AT http://www.99centguitarlessons.com/251chordvoicings.html. Explanation of 2-5-1 chords, the most commonly used jazz progression, describing the theory behind them plus where, when and how to use them. It's essential for a jazz guitarist to understand 2-5-1 chord progressions since they are found in almost every jazz song. 2-5-1, sometimes written as ii-v-i, refers to the chord progression made up from the 2nd, 5th and 1st chords in the major scale. Minor 2-5-1 uses the chords from the harmonic minor scale. 3 video lessons demonstrated close up and slowly, with printable PDF chord grids and chart.