Not everyone agrees, but the synthesizer format wars are over, and Eurorack is the clear winner. One of the most noticeable trends at this year’s NAMM show in January was the proliferation of synth modules in Eurorack format, with small manufacturers sharing the main hall with larger, better-known companies. Other modular formats remained almost entirely on the sidelines.
As instruments from mainstream companies like Arturia, Dave Smith Instruments, Korg, and Roland sprout control-voltage minijacks, the demand for synth modules is heating up, and enthusiastic circuit designers are happy to meet that demand. Alongside modules that handle individual synthesis duties like oscillators and envelope generators, some modules combine related functions to deliver all-in-one synthesizer voices, versatile modulation sources, data monitoring capabilities, and the like. In this article, I’ll focus on some of the more recent modules that handle multiple functions, including a few that haven’t started shipping at press time.
VCO ($547, 22HP)
This module combines an unusually stable voltage-controlled analog oscillator with a VCA and a 4-pole lowpass VCF. Renowned for its unique sound and named after an African eagle, the Bateleur VCO’s most notable feature is through-zero frequency modulation (TZFM), a near-mythical synthesis technique offering a broader range of inharmonic overtones than traditional FM. In the Thru-Zero position, carrier waveforms reverse direction whenever the modulator produces a negative frequency. (Yes, negative frequencies exist, though explaining them would take more space than I have here.)
In addition to four separate jacks for standard analog waveforms, a sub-octave jack emits a square wave an octave below. A knob for setting depth of the pulse-width modulation CV input supplements another for manually setting pulse width. Additional knobs control glide and FM amounts and filter input and output levels. The filter is unusual in that you can turn resonance only off or up full, making it a self-oscillating sine-wave source. Because it tracks so well, the self-oscillating filter makes an ideal modulator for through-zero FM. The optional 8HP Bateleur Expander module ($154) adds CV inputs paired with knobs for controlling filter cutoff, resonance, and exponential FM. It also supplies a VCA input with an attenuation knob.