Hi Dieter

>>That is ok, but where to place the rotary switch for multiple octave
>>switching on the frontpanel
> That's indeed our main problem ...

This is why I suggested the on/off/on switch, which usually can be
placed between two potentiometers.

The other options is to go more modular: offer only some basic CV in-s
at the core module and offer additionally an extended CV mixer, with
multiple octave switching, coarse, fine, micro tune, and several
modulation inputs with mod-amount potentiometers for log an lin modulation.

(I dont want to be nasty, but I suggested this module quite often - may
be I should do a small business for modules with underrated sales
chances ;-)))) )

Florian