> would it then not make a lot of sense to have a vca with a linear cv
> input without attenuation for the envelope, and an exponential one (or
> 2 ) with attenuation for lfo/kbd-tracking/am

For this appliaction usually two daisy chained VCAs are used: one with
linear and one with logarithmic response. This works as a multiplication of
both the linear and logarithmic amplification (i.e. if one of both is zero
the output is zero too).

> or even put a switch linear/exp next to each input

This feature will be available at the planned dual VCA (module number will
be probably A-132-3)

> stu
>
> p.s. what's the difference between exponential and logarithmic

That's mathematics. The exponential function is the reverse function of the
logarithm (like multiplication <-> division, or addition <-> subtraction).
Sometimes the terms are used as a synonym but that's wrong (even by me).
More details in your mathematics book.

Best wishes
Dieter Doepfer