Patching it all together
We’ve given you a rundown of the most used modulation sources out there, but how do they work in software? In the style of classic hardware synths, many virtual instruments feature hardwired modulation sources – the Minimoog’s Filter Contour Amount is a classic example, which instantly applies amount of filter envelope-tocutoff modulation. There’s no other way to route these hardwired controls, but they’ve usually been chosen to make the most useful assignments easily accessible.
Going further, you must have seen a synth with a modulation matrix, right? These scary-looking grids are simply ways to choose a modulator, a parameter to target, and the amount to modulate it by. Mod matrices are pretty much identical across all virtual instruments, so once you get your head around how one works, you’ll feel right at home with any synth.
Fans of megasynths Massive and Serum will be familiar with dragand-drop modulation, where the modulator (say, an LFO) has a handle placed next to it, which you can drag and drop to any control you wish to modulate, before setting the depth using another control – usually a collar around the parameter.
Check out our XILS 3 CM synth for a great spin on modulation routing – just place a pin between two axes (source and target) to set up a modulation routing.
Unipolar and bipolar
Depending on the parameter being modulated, there are two common ways values can move. A unipolar parameter moves from minimum to maximum, like a control moving from 0 to 127 or a filter moving from 20Hz to 20kHz. A bipolar control, on the other hand, still starts at zero, but moves up and down from that point, between positive and negative values.