I think he means a static fraction of a step.

MRT is correct. eg: take sound 1 and raise the pitch by 3 or 4 cents, then take sound 2 and LOWER it by the same ammount. That fattens up the sound and adds "color".

I could hear an substantial increase in fatness by the time I was up to layering not 2 but 32 detuned waveforms, but by that time my polyphony was starting to run out pretty quickly...

I messed around with it a little more and managed to achieve a pretty good version of the sound, considerably close to the original. Thanks, you guys!

yup yup I think danb bullseyed it first but do we know exactly what the obie sound is ? that piping swirly richness. Yeah it is a detuning (technically a chorusing), but it's more than that the obie circuit places the second modulation slightly out of phase in time and in amplitude as well as frequency which was unanimously agreed upon above posts.
Eb Eddie also has a DDL of roughly 230-250ms @~15-20% feedback on that delay with the effects' overall inital repeat less than 25% of dry. That makes for a dryer enhancing effect for that sound without it really sounding greasy at all. Really, (when in time)a great delay for any wave with a sharper edge. No doubt one of Mr.Templetons sonic masterminds brews, if not his E flatness himself!