This is part 2 of a 2 part article, you can find the other part here: "Modular Synthesis in the Control Room"
After reading Chris Koltay’s super fun and inspiring “Modular Synthesis in the Control Room,” I felt compelled to add a few practical notes for someone who might be new to this world.
I’ve been using modular synths in my studio for the last 15 years or so. I was first introduced to them via a large Buchla modular system in 1982 at The Evergreen State College in Olympia, Washington. I initially bought a vintage ARP 2600 for my studio around 2010 in the hopes that we could use it for a processing workflow. But it was old and cranky, and the 1/8-inch, unbalanced I/O was enough of a barrier that it didn’t integrate well with pro audio levels. My good friend, Wes Steed, left his mostly MOTM 1/4-inch Moog format two boat (racks are called “boats” in the modular world) modular set up at my studio for several years. I began to use it quite a bit to process audio when mixing and working on production, and I eventually bought it from him.
I will maintain that if you want to play a synthesizer with a keyboard, a modular setup is a waste of time. I’ve recently been loaned a Moog Model 15, and while it is an amazing, groundbreaking, historical instrument, I’m now convinced I’d never want to own one. It’s huge and, for the most part, the much smaller and more practical Minimoog can do most of what the Model 15 does (not including the secondary step sequencer modules). My point is that if you want to play a keyboard line on a synth, a modular is not the quickest way from point A to B. However, if you want to process audio in ways that no other processor can, a modular rig will open a multitude of sonic doors. I still have the MOTM rig I bought from Wes, and I have since also got into the Eurorack format. I now have one boat that is almost entirely devoted to processing.
Using modular synths as processors has a long history in popular music. Brian Eno [Tape Op #85] famously used the EMS VCS3 when he played with Roxy Music, processing the band as they were playing live, as well as in the studio on many projects. The Who’s Pete Townshend used the EMS VCS3 to great effect on “Baba O’Riley” and “Won’t Get Fooled Again.” While one might mistake these songs for using synthesizers, Townshend is actually playing long, held chords on an organ that is run through the filter of the EMS synth. The movement in the piece is not so much Townshend’s playing but rather the sound of the filter being modulated by a low frequency oscillator (LFO) using a control voltage (CV) to change the frequency of the filter. The LFO is set to a square wave, so the change in the filter frequency is abrupt and it sounds as though Townshend is a keyboard virtuoso, even though he’s not changing many notes on the keyboard. The frequency of the square wave on the LFO determines the tempo of the track. The Who’s Next episode of Classic Albums demonstrates this to good effect, and the excellent Apesoft iPad app iVCS3 [Tape Op #103] has a sample patch that emulates this trick that can be edited and deconstructed. A used VCS3 is currently more expensive than a car, but there are some excellent clones out there, such as the Erica Synths Syntrx. (A)
To revisit the terms above, it’s important to understand that every modular synth has two different types of signals present: Audio signals and control voltage signals. You can hear the audio signals, of course, but you do not hear the CV signals, even though they have an effect on what we do hear. Patch cables (or, in the case of the EMS synth, patch pins on a routing matrix) are used to route both audio and CV signals.
Before we can process anything, we need to get the audio from the DAW, console, or tape machine into and out of the modular. This was one of the issues I had with trying this with my ARP 2600. There are a lot of interface modules available in the modular world, and one of the best is the Intellijel Audio I/O. (B) It has I/O, level control, and metering for two channels of audio, both in and out of the Eurorack format. It will convert between balanced and unbalanced and 1/4-inch TRS and 1/8-inch TS connectors. A module like this is essential for any studio-based modular processing boat.
Once your audio is in the modular world, the sky is the limit, but a good place to start is running the audio through a resonant filter. This can be high pass, low pass, band pass, or a combination of all three depending on the filter design. The most common filter effect is the filter sweep heard on lots of electronic music. I find this to be an interesting way to create texture and movement in a track. One of my favorite filter modules is the Synthesis Technology MOTM-410 filter (based on the Korg PS-3100's filter), which has one input, and three outputs with three independent low pass filters. I'll run tracks, like a distorted guitar, through this, pan each filter output differently, add a subtle LFO CV to the overall filter frequency, and then manually tweak the independent filter frequencies as the song plays to create a “performance” of the processed track. I used this filter process quite a bit on the Sea of Bees tracks “Skinnybone” and “Willis.” You can also modulate a filter with a square wave LFO CV, similar to the Pete Townshend process mentioned above. Another fun process is to set up a chain of reverbs and delays on a vocal track, and then run that through a filter process on the modular so that the timbre of the reverb and delay evolve and change over time.
If you just want to dip your toes into some resonant filter effects, there are a few 500 Series filters available out there, including the sadly discontinued Moog The Ladder [Tape Op #90], which can be found on the used market. I have a pair of the Moog filters in my API 1608 console [#81], and I use them all the time.
Filtering is one of the most basic types of modular processing, but there is an ever-expanding palette of processing and CV options out there these days. Another fairly basic module is an envelope follower. This module accepts an audio input and creates an “envelope” control voltage that tracks the amplitude of the input. For instance, this can be used in conjunction with a filter to create an “auto” wah-wah effect. Arturia’s excellent MatrixBrute synth is not modular, but it does have an external audio input and routable envelope follower module, while some of their smaller synths like the MiniBrute 2 are semi-modular. The Korg MS-20 is a great semi-modular synth with a keyboard and is a good introduction to modular synthesis. It has a pitch to voltage converter that can track the pitch of an input signal, allowing you to do things like play a synth with a guitar. (This technology was repurposed into the excellent Korg X-911 guitar synthesizer).
One other practical module you’ll quickly need are mult points. These are simple modules that split the signal so you can route an audio signal or control voltage to several different places. These can be actual mult modules in your boat (C), stackable patch cables, or standalone dongle-like adapters like Modular Synth Lab's six-way Mono Patch Splitter.
Next up, you’ll likely want a mixer for your rig. There are quite a few out there that offer not only basic mixing but also CV options. I bought a Verbos Scan & Pan mixer (D) for my rig that allows for CV control of all functions, including panning. This is a great tool for setting up evolving patches that move around the stereo field, and the Verbos modules are known for excellent audio quality and build.
The other module I got for my rig (as a nod the EMS synths) is an X/Y joystick (E). Deceptively simple and complex at the same time, I like to use the joystick to add a subtle manual control to a complex patch. This can be a fun way to get the modular interacting with people who may not fully understand how it works. I’ll set up a complex patch with filtering, panning, and more, and then use the joystick to control several different parameters of the patch in real time. I'll hand the joystick over to the artist, show them how to move it, hit record, and let them interpret the processing themselves in real time. This can add some unpredictable – but usually fairly intuitive and musical – ideas to the track. I worked in this way with Joey Burns, John Convertino, and producer Craig Schumacher [Tape Op #10] with Calexico [#13] when they were working on The Thread That Keeps Us at Panoramic House.
So, I think you get the idea, right? There are thousands of modules out there now, and many of them go deep into CV-controlled DSP that's way beyond simple filtering. There are complex delays and space simulators, saturation, and any processing you can think of, and all are patchable and CV-controllable. One of my favorite modules is Mutable Instrument's Clouds (F), a stereo granular synthesis processor. (Discontinued, but available used, and clones are also available.) Both ModWiggler and ModularGrid are excellent online resources to find out more about the modular world. And Waveform is an excellent print publication for the modular world. Most importantly, have fun in the studio! 
This is part 2 of a 2 part article, you can find the other part here: "Modular Synthesis in the Control Room"
