Two separate things I thought I’d bundle into one, here. Quantizers will lock controlled-voltage signals into pitches; by default, they’ll chuck out a series of voltages that aren’t necessarily in tune. By far my favourite quantizer is the µScale by intellijel, but the Expert Sleepers Disting is also great (for many other functions, too!):
Slew Limiters are what most people might know as Glide or Portamento. Sometimes sequencers have this built in. I think the best value for money is the Pittsburgh Modular Toolbox as it does a few of the next functions too…
White Noise/Random/Sample and Hold
White Noise is found on lots of synthesisers. It’s used to synthesise hi-hats, snares, riser FX and to dirty up leads and basses. Because it is every frequency at equal amplitude, it’s the closest thing we can get to random in the analog world. The Doepfer A-118 is a good shout to do this, as is the Toolbox mentioned above which also does inversion (more on this later) and Sample and Hold.
Sample and Hold takes an incoming signal and samples it as a given interval (determined by a rate, normally a pulse wave). It’s the typical R2D2 sound or bleepy-bloppy sound a lot of people associate with 50s sci-fi sound design.
N.B I tried to knock up a diagram of Sample & Hold in Illustrator but it was harder than I thought so I’ll dedicate something to it in more depth another day.
If you’ve had any experience with computing or circuit design you might have come across logic gates, which can include AND, NOT, OR and XOR processes. These (usually) combine gate signals from different sources and output something whether or not the logic is true. This is useful for creating longer pieces of music and turning on and off sequencers.
This is best explained by Professor Brailsford from the excellent YouTube channel Computerphile. Note logic is normally discussed with binary numbers 1 and 0, which equate to on and off. For our purposes, when a note is on the gate has an output of 1 and when the gate is off the output is 0:
Here’s a handy diagram explaining the different types of logic gates:
Image © GcatWiki.
Ring Modulation, Waveshaping and other Effects
Like guitar pedals, the modular world is not exclusively sound sources and modifiers: you can have sound affecting modules, too.
Ring modulation creates metallic sounds by multiplying two frequencies together before outputting the sum and difference and is responsible for the Daleks’ voice. At lower rates it can sound like tremolo (amplitude modulation) and at more extreme values you can achieve extreme atonality. There are loads of the market, so do your research first.
Waveshaping is sort of asymmetrical distortion found in lots of modular that works by folding and clipping parts of the cycle in on themselves. There are a few options by Doepfer but intellijel and The Harvestman are among the more popular:
Other effects that are worth considering for your machine are spring reverbs (Doepfer and Befaco are a good shout), delays (the SnazzyFX’s Wow and Flutter and Make Noise Echophon are pricey but great-sounding), distortions (like Metasonix and the WMD Geiger Counter) and phase shifters:
Hat tips also go to ALM’s S.B.G that allows you to interface with guitar pedals or rack units.
Multiples are super useful modules, taking a signal and duplicating it. This is great for taking an LFO’s output and sending that to a filter, VCA and phaser, for example, or taking pitch CV and sending it to three oscillators. For these reasons, it’s worth planning at least a couple of multiples into your system.
Gate, triggers and other CV signals can be sent from passive multiples (ones not plugged into the power supply) whereas pitch CV needs to be multiplied through a buffered multiple (such as intellijel’s or this one from 4ms).