I first became interested in random harmonic generation when I heard some early computer music while in college. I found it interesting and unique in that while it was unpredictable, when the programming was handled in the correct way, the resulting “music” – if randomly generated sound can be called that – had the potential to be mesmerizing. In 1987 Michael Brecker released his album “Michael Brecker” and one of the hallmark sounds on that disc was his use of the EWI (Electronic Wind Instrument) and synthesis to create an amazing palette of sounds. One of the most interesting things he did was to use a feature of the Oberheim Xpander module to randomly rotate through a series of harmonies. It works something like this:
The Xpander had a setting called “Rotate Mode” with 6 voice polyphony. Michael was able to turn that into an amazing harmonic tool by creating two zones on the synth, one with two “static” voices set to re-trigger and one with four rotating voices in rotate mode. I have recreated this functionality in Logic’s environment with many additional features and expansions on the original idea.
More in depth information is available here.