Over the weekend, I had a wild hair up my ass to buy some kind of FM synth off of Reverb.com, because I needed a multitimbral sound source to get some use out of the 8 MIDI tracks of my Octatrack, which I powered up after a long work-filled hiatus. I wanted the FM sounds of the early 80’s

Back in the late 80’s and early 90’s we had a Yamaha TG33, which was a multitimbral, digital FM synthesizer with a joystick for doing vector-based modulation. Like its cousins of the time, the TX81z, the TG55, SY77 et al, it had the execrable 2-line LCD display making any kind of artistic sound design workflow tedious. We (and I mean my old band, I.E.C.) mostly got by on presets, and that was a little before the time of PC-based GUI editors and configurable hardware programmers.

Since then, I’ve learned a little more about FM synthesis, but I can still safely say I know jack shit about it on an instinctual, muscle-memory level, beyond the idea that addition of waveforms together results in some interesting and very familiar sounds. Try googling “Lately Bass” or “Solid Bass” sometime.

FM synthesis is also largely responsible for most of the sci-fi and action B-movie soundtracks from the 1980s, which begat the electronic subgenre we now call “Synthwave.” There’s a lot of crossover between synthwave and metal fans, because synthwave is essentially metal using electronic instruments.

But I digress.

Not really wanting to spend ~$250 on a PreenFM2, or the horrendously inflated prices for old rack mount FM synth modules, I turned once again to my old friend, the Raspberry Pi 4b, and the Zynthian project, a fully open-source, open-hardware synth platform. It’s not cheating, because the type of digital synthesis found in keyboards like the DX-7 is kind of what computers do well, and there are several good engines for replicating the circuitry and functionality of those ancient machines.

Dexed is a DX-7 emulator, an open-source plugin for most of the architectures out there, including LV2 in linux. It’s included with the Zynthian OS download, and you can edit patches on another computer and upload them to the Zynthian patch storage, or if you set up your X11 connection correctly, you can edit them right on the Pi.

The end result is a functional multitimbral synth with a more or less intuitive UI, barring the dangling encoders shown in the video. In addition to the encoders, touchscreen functionality is also available. It’s controlled by MIDI over USB, which makes it perfect as a sound module for the NDLR.