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Vermona TwinCussion

Eurorack Percussion Module
Published October 2016
By Paul Nagle

Vermona TwinCussion

Vermona know a thing or two about analogue percussion — their DRM1 is still going strong in its 16th year of production! As the name suggests, TwinCussion comprises a pair of voices (A & B), both slightly different and capable of independent operation or cross-patched interaction. Consistent with all Vermona products, the feeling is of sturdiness and quality throughout, with extra ‘care’ points earned by the inclusion of a printed manual and plastic washers to keep rack rash at bay.

Each voice consists of a single VCO with three waveforms, plus a VCA and simple envelope. The first sports sine, triangle and square waves while the second drops the triangle in favour of noise. Regardless of selection, all waveforms are freely available for modulation purposes.

Voltages above +2V are sufficient to trigger the envelopes, both of which deliver a maximum of 5V. While you might ordinarily choose dual-voice operation, a single connection to EG1’s gate input is enough to drive both simultaneously. For audio connections, a mix of A&B is available at B’s output. By inserting a lead into output A, you gain the option of fully independent external processing.

Given that they’re designed specifically for percussive roles, the VCOs don’t track 1V/Oct accurately. They offer two operating ranges — Hi and Lo — that translate to 20Hz to 200Hz, and 100Hz to 3kHz respectively. Via CV input these values can be driven upwards as high as 5.6kHz. The noise generator responds to the Hi/Lo settings too, the tune control sweeping an internal filter to offer a range from dense and roaring to thin and blue noise. However, neither the envelope nor oscillator CV input has any effect on the filter frequency.

The envelopes are internally routed to pitch and VCA level, but the connections can be overridden by patching, whereupon the knobs switch to attenuating the incoming CV. Sweeping oscillator pitch is an important component of many analogue drum voices, notably kicks, toms and snares. Unusually for a percussion module, voice A’s envelope has a variable attack — from a snappy 0.1ms to 2s. This carefully tailored response proves to be a significant bonus; it can, for example, tame the initial click of a bass drum, add cuica-like wobbles or turn hi-hats into shakers. The decay’s exponential curve is well-suited to chirpy Kraftwerk zaps and while the first EG’s maximum decay time is 5s, the second reaches a languid 10s, plus it has an extra twist in the form of CV-controlled decay. (CV inputs accept ±5V.)

Since the second voice features noise, it’s the ideal choice for hi-hats in a hurry. Draft in EG2’s CV input and you can simulate a hi-hat opening and closing. So while there are no built-in dynamics, decay modulation by a slow-moving triangle wave can introduce welcome movement to those static patterns. If it’s actual dynamics you require, you’ll have to route the EG’s output through an external VCA under velocity control before routing it back to drive the TwinCussion’s own VCA.

Whenever I start to synthesize drum voices, I gain fresh respect for the designers of analogue drum machines, old and new. By the manipulation of envelope, initial pitch and pitch sweep, it’s surprisingly painless to rustle up a swathe of favourite voices on the TwinCussion. Voice A serves up a pretty decent bass drum with a sine or triangle wave selected, pitched to taste and a small amount of pitch sweep applied. A square wave will yield a harder, more overdriven type of kick. Voice B could then be your variable-decay hi-hat.

Additional sonic interest is achieved by cross-patching. You’re not necessarily limited to the same decay time for the pitch as the VCA, and if you modulate the pitch with waves from the companion voice, metallic FM tones ding into being. Admittedly, I’ve so far failed to nail a convincing cymbal, but after only a few days I was pretty confident of summoning bass drums, snares, claves, cuica, rimshot, toms, congas, hi-hats, shakers, metallic percussion such as triangles and bells, plus numerous blip- and boink-type hits. The results become noticeably more organic when a voice’s shared components are triggered separately, eg. the body and noise elements of a snare.

At just 24hp the TwinCussion packs in quite a punch, either as a single composite voice or a double-whammy twin. Although lacking the components for really wild and intricate sounds, this unassuming little module delivers a heap of useable drum machine standards with just 10 knobs and four switches. It’s an excellent way to add analogue percussion to any Eurorack system.

Published October 2016