I created this plucky microtonal patch by using the cross modulation on the Roland MKS-80 to effectively put the instrument into an instable, out-of-tune state. I mentioned in my previous entry that cross modulation is a form of frequency modulation or FM synthesis made famous by the Yamaha DX-7. My curiosity about this technique led me to an article in Sound on Sound from 1994 titled Exploring Analogue (Part 2) by Steve Howell. In the article Howell states,

“…take the output of one oscillator (Osc A) and feed it into the control input of another (Osc B). As the modulation level at Osc B’s input is increased, so its tonal quality becomes progressively nastier. In fact, in the absence of a ring modulator, cross-modulation can be used very effectively to create clangorous bell sounds and the like. But be warned! Because the tuning stability on old analogue synths leaves much to be desired, the oscillators don’t track too well, and a sound that is perfectly tuned on C3 may well have disintegrated by the time you get up to F3.”

On the Roland MKS-80 the tuning stability is pretty good, but it does use VCOs (voltage controlled oscillators), so they won’t track as well as DCOs (digitally controlled oscillators). This imperfection is part of what many of us find attractive about analogue synthesis, and what made it possible for me to produce this bizarre, out of key, yet delightful sound.

Cross Modulated Microtonal Improvisation