[sdiy] Glide question

[Olivier Gillet]

There are two ways of doing glide/portamento:
- "constant time" in which sliding between C3 and C5 takes as much
time as sliding between C3 and C4.
- "constant rate" in which sliding between C3 and C5 takes twice as
much time as sliding between C3 and C4.

I might be wrong about this, but a RC filter on the CV will make it
constant time. For voltage control, any VCF design will do - glide is
just a filter/slew limiting of the pitch CV signal. Actually, a filter
with resonance / ripples (which will translate into overshoot in the
time domain) might make for a cool "natural" (?) portamento effect
simulating a singer or instrumentist moving up and down zeroing on the
target pitch.

Another interesting variation is to have distinct RC constants for the
up and down segments, like on this thing which looks like a nice
portamento factory:
http://www.synthtech.com/motm820.html