In short, what Thor said...
The trick of using separate (sharp) tuned operators to make the higher order harmonics of the bass (wound string) notes works well, then using either zone detuning (Montage) or the Microtuning abitlity of DX7II/TX802 to 'stretch' the upper ranges can give some nice results. ?But that's kind of a special case and not a lot is needed.
In my experience there's typically no need for, or improvement gained by 'stretch tuning' FM sounds.
Manny
