Someone in a synthesizer forum said that this would be useful. Modulation capabilities vary quite widely between synthesizers but here’s an idea of what’s going on.

Here are two prepatched synthesizers:

You may recognize Subtractor from other tutorials. They’re called “prepatched,” because the connections between modules are called patches and all the connections possible in these synthesizers have already been made.

Both synthesizers can have multiple destinations for the mod wheel and velocity but Subtractor’s LFOs and mod envelope can only control one parameter at a time, while Malstrom’s LFOs can control multiple parameters at a time but there are fewer parameters to choose from. (Again, modulation capabilities can vary widely.)

Here’s a synthesizer with a mod matrix, with some of the slots filled in, just as examples:

Each of the control sources can be assigned from their own section and from the mod matrix, with a long list of destinations. Further, control sources can control each other; note that the mod envelope is controlling LFO 1. (Gordon Reid gives an excellent example of why you might want to control LFO modulation with an envelope at the bottom of this page.) More subtly, you can extend the range of any control on the panel by routing a constant signal to it. What’s important to recognize is that the routings are functionally the same, regardless of where they’re done.

In practice, there’s an awful lot that can be done with Subtractor’s modulation routings but I often use another synth, because it’s flexible to the point that I don’t really need to think about what it can and can’t do. Here’s Thor, also with some example routings:

Thor is “semi-modular,” note the different oscillator and filter types, and has a larger, more complex mod matrix than Antidote’s.

Unlike Antidote, the LFOs and mod envelope can only be routed through the mod matrix but the mod matrix can also route and process audio and even convert external audio to cv (different connections and sample rates, in Reason) and vice versa. This is similar to programming a modular synthesizer but still with the convenience of note and gate controls being prepatched, along with a basic oscillator>filter>amp signal chain.

Personally, I like having all of my modulations in one place, just as a workflow feature. As stated, not having to remember which control sources can modulate what (since any source can be routed to any destination) and having the luxury of using one source or destination in multiple routings also free up space in my head. These are my reasons for loving Thor’s mod matrix, despite my rarely needing any real jiggery pokery.

But jiggery pokery can be fun:

Here’s an example of a patch with some more advanced cv routings. From top to bottom:

The gate is also triggering the sequencer (advancing one step for each note). The sequencer is panning each voice as it’s triggered. (Because Thor doesn’t have that kind of width function built in – Reason’s like that, with the main feature being its ability to overcome its lack of features.) Oscillator 3’s amplitude is being keyscaled, so that higher notes have less sub oscillator in them. To shape the keyscaling, I’m essentially keyscaling the keyscaling, turning a linear function into an exponential function. (This also works with envelopes; see the first Thor image.) I’m using the mod envelope to increase resonance at the beginning of each note. (Note that I could have used just one row on the right side, since there are four rows with two destination slots.) I’m controlling the built-in delay with LFO 2 (channel), for an additional rhythmic effect.

All mod matrices are not created equal, so you’ll need to put in time with your own synth to see how far it will go. I’m partial to Thor’s design with scale slots, as I find it more intuitive than modulating a modulator, but that’s partly because I learned synthesis with Thor. If you’re at the stage where this crash course is helpful to you, I recommend spending some time going through your synthesizer’s factory patches; you should now have a better idea of what you’re looking at and why. If there’s a mod matrix use you’d like me to elaborate on (it was hard to choose examples), leave a comment.