Octave range shifter, similar to Moog Mini moog, U-HE Diva etc.

Hi,

Im currently trying to create a subtractive synthesiser, i am working on the oscillators at the moment and i hvae created a waveform selector that works fine. Im now trying to replicate an octave range selector and pitch shifter similar to that of most subtractive synths but specifically based on U-he Divas triple VCO oscillator.

any help for tips would be amazing!