MOTM

I may have missed this completely, but aren't you talking about simply
sweeping the harmonics of a waveform using a bandpass filter?

Basically you feed a long, sustained, rich-harmonic waveform into a bandpass
filter (sawtooth or pulse) and then sweep the filter's cutoff frequency so
that the filter "picks out" one harmonic at a time (within the slope of its
cutoff). The sound will seem to "jump" because you are sweeping discreet
harmonics of the source waveform.

A sawtooth at middle C, with the cF all the way "down" and then slowly swept
"up," will first give you a dull sound at middle-C, then jump up an octave,
then jump up a fifth, then jump up a fourth to the next octave, then up a
[roughly] major third...

Essentially you use a bandpass filter for this, but a good, 4-pole LPF with
the resonance cranked almost to oscillation creates a very tight
bandpass-like response near the shoulder frequency that will do the same
job. I've heard this effect even using the Triple-Res filter, too, though
it's not as pointed as using the Hi-Res LPF.

You can create richer waveforms by using multiple oscillators or other
tricks, but you "muddy" that jumping effect that you're talking about
because you no longer have that nice, static separation of partials.

I could have misunderstood this whole thing, but I thought that was the
original question. Then folks started talking about using EGs, Sample & Hold
circuits, etc. If I understand what you want correctly, all of that is the
long way around.

Thought I'd throw my two cents in.