Idea for an envelope generator

[Christopher List]

I was thinking about something for an n-step envelope generator today and I 
wonder if anyone's tried it (I've got so many circuits in the works now that 
it'll be a while before I get to play with this one).

Suppose you had a two channel sequencer (analog, of course). 
Make channel A your voltage levels and channel B is your delay times. 
You run the output of channel B into the CV of a linear VC slew limiter. 
You split channel A. One line goes into the input of the slew limiter. The 
other line goes into two op-amp circuits. One adds a millivolt, the other 
subtracts a millivolt - these two signals become the high and low reference for 
a "window comparator" (two comparators and a NOR gate, I think). The output of 
the slew limiter is your envelope output and also gets routed into the input of 
the window compator. Lastly, the output of the comparator gets routed back to 
the trigger input of the sequencer.

Is there an easier way of comparing two voltages?

I haven't worked out the logistics of starting / ending the process - any 
suggestions?

Has anybody tried this? - I haven't built a sequencer yet, but it seems like it 
would be a cool mod for an existing sequencer. You could just put in an "auto 
step" switch which would route the signal through this circuit and 
automatically step the sequencer as it reached each value...

-CL