We discussed the history and recent resurgence of analog music synthesizers in Part One of this series, and briefly touched on some currently manufactured gear that offers basic facilities for pitch, parameter, and clocking control via control voltage. In this installment, we’ll dig deeper into the what, whys, and how-tos of this electrically based method for interfacing sound modules, and discuss several scenarios that may provide the basis for your own musical experimentation and inspiration.
It Takes Two to Tango
The most basic connection that can be made between two synthesizers is to set them up to play in unison. More than simply doubling the power of a basic synth voicing, unison play allows for the creation of complex timbres—results that may not always be possible with a single synth voice. In actuality, this is similar to how most multi-oscillator synths work, except with those synths, all the components needed for a sound are generated and routed internally—imagine a hearty cassoulet with all the ingredients simmering away to perfection inside a common cooking pot. But much like a tasty meal, a simple accompaniment—in this case an extra synth voice—can lend added dimension to otherwise basic sonic fare.
"The most basic connection that can be made between two synthesizers is to set them up to play in unison."
Two of the most complementary flavors of analog synth come from French manufacturer Arturia, with their MiniBrute and MicroBrute. Both are powerful, single-oscillator monophonic synths with the ability to mix in relative levels of different oscillator wave shapes. This provides the user with a clever way to sculpt complex, harmonically rich wave shapes from a single, shared oscillator. While that’s indeed a neat little trick to get more mileage out of a single tank of gas, so to speak, it’s still no match for the horsepower that can be generated with a true multi-oscillator mono synth like the Minimoog or ARP Odyssey, which have signal paths with three and two discreet VCOs, respectively.
When matched against the prices of vintage Moogs and ARPs, owning both Arturia synths isn’t out of reach for a certain level of enthusiast. And for those lucky enough to own both, a first-class ticket to fat, multi-oscillator bliss awaits! By simply connecting the MiniBrute’s Pitch CV and Gate outputs to the MicroBrute’s Pitch CV and Gate inputs via mono mini-jack cables, notes that are played on the Mini’s keys, or via an external MIDI controller (both synths are serviceable as MIDI to CV convertors), are tracked by the Micro’s sound engine. Route the Micro’s audio output to the Mini’s external audio input and you’ve got a dual-oscillator monster capable of ripping leads and thunderous bass tones. Experiment with various combinations of waveforms or harmonic and inharmonic tunings to create buzzing, metallic tones or sweeping, flange-like effects.
That Syncing Feeling
One of the coolest applications of control voltage is as a tempo-based clocking pulse for a synthesizer’s arpeggiator or step sequencer. Before the advent of MIDI clock sync—a common standard for synchronizing recent drum machines, keyboard workstations, and DAWs—compatible sound-generating devices were set up to play back rhythmic sequences in parallel through the use of periodic voltage triggers. In the early 1980s, Japanese electronics manufacturers, such as Roland and Korg, equipped many of their drum machines with trigger outputs, allowing a would-be one-man band to start pre-programmed sequences on synthesizers with the simple press of a Play button. This may seem primitive in this age of DAWs with unlimited sequencing tracks, but some musicians are discovering that limitations like these can breathe new life into the music-making process.
"You’ll see that the synth sequence now plays in perfect sync with the drum machine’s tempo."
Spawned by the immense popularity of Roland’s classic “X-0-X” boxes of the 1980s, including the TR-909, TR-808, and TB-303, Korg has released the diminutive Volca series of trigger sync-able groove boxes. Volca Beats, an analog drum machine modeled in the style of booming bass thumpers like the TR-808, is particularly well suited for driving musical sequences on either of the previously discussed Arturia synths.
Let’s say you’ve programmed a groovy 4-bar bass line using the MicroBrute’s built-in step sequencer and want a snappy little beat to play in time with your new creation. This is easily achieved by connecting a mono mini-jack cable from the Volca’s Sync Out to the Brute’s Gate In. When Play is initiated on the Volca, a sync trigger is sent on every eighth note of a bar, advancing the Brute’s sequencer in eighth-note increments. Because the MicroBrute’s sequencer advances steps in 16th-note increments, some care will be needed to program rests on every other note to achieve a bass line that does not play at double the Volca’s tempo. You’ll see that the synth sequence now plays in perfect sync with the drum machine’s tempo. Now try slowing down or speeding up the tempo on the Volca—the sequence should stay in perfect time and locked to the beat.
Movin’ & Groovin’
As entertaining as it is to set up a repetitive synth line that playfully putters along to a steady beat, a static sequence can be made far more interesting by creating subtle or dramatic modulations over time. An interesting companion to the MicroBrute is Arturia’s new BeatStep analog sequencer/controller. This low-cost device is a viable alternative to classic CV/gate step sequencers such as the Doepfer MAQ16/3 and the ARP Sequencer. With its CV and Gate outputs and 16 rotary encoders and LED-lit pads, the BeatStep can easily be used as a note sequencer for nearly any voltage-controlled synthesizer. But there’s nothing preventing you from using its CV Out to apply sequenced voltage changes to non-pitch parameters on the MicroBrute and other synths.
Since we’ve already set up a nice beat and sequenced bass line, let’s try creating some further movement to the sound by modulating the Brute’s filter cutoff frequency. In addition to its voltage outputs, the BeatStep happens to be equipped with a MIDI Out, allowing us to send a MIDI clock signal to the Volca’s MIDI In. This will lock the Volca’s tempo to the BeatStep, while simultaneously triggering the bass line sequence on the MicroBrute via the Volca’s voltage Sync Out. This allows us to connect the BeatStep’s CV Out to the Brute’s Filter CV In jack so that now when we apply voltage changes to each of the 16 steps, the filter opens and closes in time with the sequence. It’s also feasible to modulate any of the other parameters on the Brute’s Modulation Matrix, opening up possibilities for intriguing, ever-evolving timbral changes.
Press ‘Play’ on the Volca Beats.
Sequences on both machines now play in perfect sync.
As you can see, control voltage gives a uniquely hands-on window into the ins and outs of synthesis, while providing immediately satisfying results that can be applied to your sound design and music making. In the final installment in the series, we’ll discuss more advanced setups that bridge CV/gate-enabled gear with the brave new future of DAWs and digital audio. Stay tuned.
Click here for Part One of this series.
