Glad U found the link interesting.
The complete article was in Polyphony LabNotes long time ago.
As far as "range", I believe the EK7 was for a 0-5V signal uses for preset saving on the Paia Proteus.
The knobs/pots on the proteus were grouped into banks and one 8bit word was created with
TWO EK7 circuits. btw, I have and original Proteus.
U could easilly "re-range" the input to be 0-2.5V by adding a x2 amplifier in front.
Or, 0-1.25V range by adding a x4 amplifier in front.
Then, U could always "fold" the bits by feeding some bits back thru XOR, OR and/or(pun) other gates.
It's all gonna come out square waves just by the digital nature of the signal.
Run the squares thru lowpassfilters (LPFs) to squeeze out the sines

Keep breadboarding....
