Coltrane changes (sometimes also termed the Coltrane matrix or cycle) refer to a progression of substitute chords employed by the great jazz saxophonist John Coltrane. These substitute chords have now become a commonplace harmonic device with many modern jazz musicians. Coltrane began experimenting with these chords in the 1950s and continued his work with the cycle on his legendary album ‘Giant Steps’ in 1960. The substitute chords Coltrane used for his cycle are perhaps best explained by comparing a standard II V I progression with one modified to include his matrix. A great example of this is his re-harmonisation of the Miles Davis composition ‘Tune Up’, which he re-wrote as ‘Countdown’. Illustrated below (in the first stave) is the first four bars of the composition ‘Tune Up’ which features a II V I progression in the key of D major. In the second stave you can see the application of the Coltrane cycle over the same sequence.