Oh sample and hold… why did I wait so long to make you part of my life?
I finally broke down and ordered a Doepfer A-148 dual sample and hold module. (It does track and hold as well, just switch jumpers on the back of the module). It arrived today and I am extremely happy.
The basic function of an S&H (sample and hold) module is to take a sample of an incoming voltage whenever it receives a trigger (or gate) signal. It then holds whatever value that incoming voltage was at when it was sampled until the next trigger. It really is that simple.
The classic usage of a sample and hold function is with white noise as the sample source. Whenever a trigger is received the S&H will produce a new random value. Plug this random value into a v/oct input and we have a sample and hold melody. But you can do more with the S&H white noise configuration than that. Take a listen to Divkid’s overview of Mutable Instruments Warps module. That was the moment I knew I would one day need a sample and hold. He didn’t use the sampled and held noise to create a melody, but modulation. There’s absolutely nothing wrong with a S&H melody, but to me, the true beauty lies in modulation.
Sometimes, I’m frustrated by the modulation of classic envelopes and LFOs. I don’t always want a smooth control voltage. I want my voltages stepped and clocked so that they can change in time with a sequence (or even keyboard controller). But I don’t want something as boring as a square wave LFO which is quite blandly high or low (but nothing in-between). And I don’t always want pure randomness. Sample and hold lets me create a stepped voltage from ANY voltage source. Envelope? Sure. Sine-wave? Sure. Ramps and saw? Yep, them too! (which reminds me, I gotta play around with those for some nice staircase effects) Right now I’m feeding one the sample and hold inputs a very slow, smooth random voltage. It gives me a nice blend of variety and consistency. Slow, steady and stepped change over time.
You can feed it any sort of sample voltage that suits you. Get as crazy as you like, but don’t forget the trigger/gate source. Any will do, but if you feel like getting a bit more creative I recommend: clock dividers, Mutable Instruments Branches, logic modules, or even random gate sources (A-149-2 for example). These allow you to keep them from triggering with every single tick of the clock or press of the key. They become somewhat random, or carefully crafted timed events, bringing well placed bits of spice to your patch.
You can do more (sample rate reduction of audio) but this is the bread and butter of sample and hold, and it will suffice for today. If you don’t have a sample and hold somewhere in your rack, I strongly recommend getting one. It’s a powerful, simple and useful function. Oh and they tend to be small and inexpensive. 4hp and $80 USD for two channels from Doepfer’s A-148, or Mutable Instruments Kinks provides a S&H normaled to a noise source (among other functions), it’s 4hp and $110 USD.