[sdiy] Gated VCO cycles

[Peng]

I was reading the VCO section in the EMU Modular Sythesizer Operation Manual Retrospective by Dave Rossum (lost the link, it's a PDF file) and came across an interesting feature. A gate input where the VCO is off until a gate is received, then it starts it's cycle. when the gate is turned off the VCO finishes it's cycle before going off (see page 7). I want to implement this feature in some of the VCOs I'm building, but I'm not sure how to accomplish this. Should I be looking at the switch in the VCO core?
  I'm thinking this gated on/off could solve two problems I have with my synth. One being: how to keep my LFO in time with live impro drums ? For example: I'm using a +/-5V sine to modulate cutoff on a VCF. On every key gate I would like it to modulate the frequency up before (reset). This way, if I get the lfo speed close to the drummers tempo the modulation sounds better (more locked).
 
  Second problem would be the sharp clicks and pops I get when playing low bass lines, especially when the waveform has low harmonic content, like a sinewave. They kinda come and go randomly with note ons and sometimes note offs. I notice this with other synths with free running oscillators and even a lot of software synths. Are these clicks/pops the result of non-zero cossings (sorry for the sample editing speak)? I can supress the clicks with EQ but that's not always desirable. 
 
  Any info, advice, comments,ideas are desperately needed and greatly appreciated.
 
Thanks
Peng
 

		
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