[This article first appeared in the January 1980 issue of Contemporary Keyboard magazine.]
Harmonic alteration is an important aspect of traditional jazz improvisation, yet many pianists are at a loss when they attempt to extemporize new harmonics while playing a familiar tune. The temptation is to work out just one interesting progression for each tune and then concentrate on melodic invention. But it can be just as challenging to practice improvising on the harmonies while keeping the melody relatively constant.
You might find it interesting to play through the ten examples I have given below of harmonic substitutions on the first eight bars of "Liza." Play the melody straight each time, then improvise through all ten segments without stopping. Analyze the segments, recombining their parts to make more, and devise similar substitutions of your own.
You may also wish to compare your harmonies with those on recorded versions of the tune. You could start with the Herbie Hancock/Chick Corea duo album In Concert, the Art Tatum solo version on Masterpieces Volume II, and others you have may have readily available.
Chord substitution is not only a musical challenge in itself, it can stimulate new ideas for melodic invention. Revitalizing your harmonic vocabulary can go a long ways towards giving you a whole new approach to the keyboard.