Step by step

3. FM synthesis with VCV Rack

1 For our final digital patch, we’ll look at one of the most popular and powerful forms of digital sound generation: FM synthesis. Start by clearing the rack. For this patch, we’ll need an Audio module, so let’s grab one from the Core collection. This time, we’ll use our audio interface drivers, rather than those of a DAW.

2 We’ll need a VCA, too. And why not throw in a Delay module for sweetening? We’ll route the top Out of the VCA into the Delay and the Delay’s Out to Inputs 1 and 2 of the Audio module. Rather than using a MIDI module to drive our patch, let’s choose a SEQ-3 module from the Fundamental category.

3 Let’s drop in our first FM module. For this, we’ll use Bog Audio’s FM-OP. This is a single FM operator complete with a built-in envelope generator. We’ll route its Out to our VCA’s topmost In jack. It generates a simple sine wave. This will be our carrier. Let’s run a cable from the SEQ3’s Gate Out to our FM-OP’s Gate In.

4 There is a tiny button labeled Env just to the lower-right of the FM-OP’s Level knob. Click it to lash the module’s level control to its internal envelope. Now the sequencer is triggering the envelope. Set FM-OP’s Attack and Sustain to 0, Decay to 9 o’clock and the Release to 1 o’clock for a percussive envelope.

5 Let’s add a second FM-OP. This will be our ‘modulator’. Usually, FM synths offer four or six operators, but we can make a nice percussive sound with two. We’ll patch this new FM-OP’s Out to our first one’s FM Input. Reduce the pitch of our second FM-OP to 10 o’clock. Crank the first FM-OP’s Depth knob up full.

6 Patch SEQ-3’s Gate to the second FM-OP, and route the sequencer’s Row 1 to our carrier and Row 2 to our modulator and tweak the knobs for both rows. A classic metallic FM sound! Activate Env switch for the modulator FM-OP’s Level and tweak envelope settings for a punchier sound. Get experimenting!