Wired for Sound: A Brief History of Control Voltage


Modern-day musical synthesizers offer a staggering array of options for control of parameters, note sequencing, and interfacing with hardware sound modules and software DAWs and plug-ins. Among these, the now-ubiquitous MIDI (Musical Instrument Device Interface) protocol has been around since 1983, while the network-optimized, less widely adopted, OSC (Open Sound Control) has been in use since the late 1990s. These standards have empowered both studio wizards and bedroom producers to wield a formidable arsenal of sound tools and sculpt them into the most complex musical orchestrations possible. So it’s interesting to note that droves of tech-savvy musicians are rediscovering the joys of control voltage, a relatively primitive method of interconnecting synthesizer modules, which dates back to the knob-laden, patch-panel-strewn modular behemoths of the mid-20th Century.

Moog Modular, 1965. From the Moog Archives.

In 1945, Canadian composer and instrument builder Hugh LeCaine created the Electronic Sackbut, widely considered to be the world’s first voltage-controlled synthesizer. But it wasn’t until the groundbreaking designs of Don Buchla and Robert Moog in the 1960s that basic synthesizer components such as oscillators, filters, amplifiers, envelope generators, and ring modulators were commercially sold and assembled piecemeal into sound synthesizing systems—primarily for use in acoustic research centers and academic music studios.

The beauty of these systems was their utter flexibility; a composer (or more accurately an engineer in the guise of a composer) would determine which components would be used, and how the signal would flow between them. After careful consideration was made on how best to achieve a certain sound timbre, the necessary modules were manually patched together with cables. And with modules encompassing not just audio signals but also control and logic functions—with many overlapping between all three—no limitations needed to be placed on signal routings. This allowed, for example, random voltages from a noise generator to be captured by a sample and hold circuit, and sent to control the clock rate of a step sequencer. You could also patch an LFO (low frequency oscillator) to modulate the cutoff frequency of a VCF (voltage-controlled filter)—this created possibilities for all manner of Sci-Fi-inspired weirdness.

Despite modular synthesizers being used by musicians throughout the 1970s, from R&B and jazz stars Stevie Wonder and Herbie Hancock to Berlin School electronic artists such as Tangerine Dream and Klaus Schulze, they were largely supplanted in popularity by hard-wired, fixed-signal-path monophonic synths such as the Minimoog, Arp Odyssey, and Oberheim SEM. While these classic synths offered far less flexibility than most modular systems, they were prized by musicians for their relative ease of use and rich sound. And so it went through the '70s to early '80s: analog synthesizers and the systems for interconnecting them became more simplified, with patch points appearing for basics such as pitch and gate (note length) and, less commonly, FM (frequency modulation), filter envelope, external audio input, and others. When MIDI and digital synthesizers such as the Yamaha DX-7 finally arrived in the 1980s, the writing was already on the wall: analog synthesizers were about as passé as pet rocks, leisure suits, and 8-track tapes.

Then something interesting happened… analog synthesizers regained their mojo in a big way. Spurred by the rise of techno and house music in the mid-'80s and, later, electronica and EDM in the '90s and '00s, musicians, producers, and DJs began experimenting with analog equipment that had for years been languishing in bargain bins. These intrepid explorers of sound devised a futuristic musical vocabulary with even the most primitive of tools, manipulating sonic parameters that had previously been overlooked in traditional rock and jazz contexts. Instruments like the Roland TB-303 and the Korg MS-20 became prized not only for their aggressive, up-front sound, but for their interfacing capabilities with complementary equipment (especially the MS-20 with its semi-modular patch panel, designed to allow the user to override the synth’s internal hard wiring). This trend toward modularity has not been lost on today’s synth manufacturers, with most of the current crop of monosynths offering, at minimum, CV (pitch) and gate (note length), and many, such as the Moog Minimoog Voyager, Arturia MiniBrute, and MicroBrute, and Korg’s reissued MS-20 Mini, offering an array of patchable parameters.

It’s clear that the resurgence of affordable, patchable analog gear is in full swing. And it’s not just monosynths, but guitar pedals and other effects units that are being designed with interfacing in mind. Even modular systems are back in vogue, with dozens of boutique manufacturers designing specialized modules for the popular Eurorack format. While this kind of gear is not meant to replace workstation keyboards or instrument plug-ins inside your DAW, it can open up creative avenues that you may not have considered. And the hands-on appeal of twisting synth parameters or firing up a step sequencer from the press of a button on a drum machine is undeniable, and may prove to be a welcome break from mousing around a virtual instrument or menu-diving inside a digital keyboard.

In future installments, we’ll discuss basic interfacing scenarios with CV/gate-enabled gear and ways to integrate such equipment within computer-based setups. Stay tuned for more!