Hi Sintek.

I'm not a technician. I too have a hard time to get my head around, what's excactly going on.

I don't understand, what you mean with inharmonic and harmonic in this context. I think perhaps you are mixing things up.

In this context exponential is a curve, that seems to be the 1 volt pr octave as you say. The liniar is a line.

I understand whay you say it look like the linear is exponential and the other way around.

If you take a positive modulation amount for the exponential and then a negative modulation with the same amount, then you get the same pitch interval up or down, when you add the same modulation.

This is not the case for the liniar, as the negative pitch modulation with the same modualtion amount as a positive, will give you larger interval than in positive direction.

This you could think is showing that the liniar is working as a exponential, but is'nt it actually the other way around, so it work as it should, as the exponential modulations give the same interval on a the pitch no matter it's a negative or positive modulation?

Perhaps this can explain?:

https://www.allaboutcircuits.com/projects/diy-synth-series-vco/ - Notice the output is exponential.

I don't understand is why the linear input is/ has to be so steap.