The Polygogo is the first Eurorack offering from German company E-RM Erfindungsbüro. Weighing in at a hefty 32HP the Polygogo is billed as a "Stereo Polygonal Oscillator" and according to E-RM is "based on complex two dimensional amplitude shaping of sine waves". If that kind of description raises nightmarish visions of endless programming and menu diving, fear not, as this seemingly complex and dense synthesis method has found a fantastically intuitive and user-friendly home in the Polygogo.

Featuring a one-slider-per-function interface, a gorgeous screen, and stereo outputs, the Polygogo is an immediately approachable—and more importantly—playable module. The controls are centered around the idea of generating sounds and timbres based on different polygons along with a few methods of distorting those shapes for harmonic and timbral sculpting.

On the left hand side of the generously spaced and cleanly designed front panel are a series of controls each with identical groups of slider, knob, and CV input. From left to right they are pitch [v/Oct], ORDER, TEETH, ROLL, OP Ratio, and OP amount. On the right side of the module is a large OLED screen with buttons below it labeled CYCLE, REGULAR, and OP Ratio. Below that are attenuators and inputs for FM in, FOLD, a SYNC input, and the stereo outputs [labeled X and Y in keeping with the sound visualization, and interestingly the Polygogo can also drive laser synthesis/visuals directly via these outputs].

ORDER controls the number of sides on the polygon, ranging anywhere from a flat line to an almost smooth circle. The Polygogo will smoothly transition between the number of sides—morphing between them with one open face while traversing towards each regular closed shape—and has the practical effect of introducing various harmonics and overtones to the signal. This can be changed by pushing the REGULAR button, which forces the polygon to maintain a closed shape and will jump between polygons with different numbers of sides [i.e. directly from triangle to square to pentagon and so on].

In general, the greater the number of sides in the polygon the smoother the waveform created; reaching a near sine wave when at a full circle. The TEETH parameter also affects the polygon's sides but instead rotates or angles the sides inward—think of a stop sign morphing into a windmill and you get the idea—again pushing different harmonics and overtones to the fore. When fully engaged, TEETH can collapse the sound to twitchy ticks and thin electrostatic like pips and pops. With its modulation input, TEETH can even be used as a kind of dirty VCA. The related FOLD knob allows you to further manipulate the output by extending and reflecting the sides of the polygon off of a boundary back toward the center of the screen and leads to increasingly distorted tones or wave-folded like effects. It's worth noting that the FOLD parameter has no effect when the TEETH slider is all the way down, a feature implied nicely in the faceplate graphics. Finally, ROLL rotates the shape over time from speeds ranging from a crawl to warp speed, and produces pleasing stereo field variation, with a kind of phasing effect at slower speeds and all-out noisy thrashing at the highest setting.

The Polygogo also does FM and features a built-in operator and dedicated controls for the ratio and amount of modulation. The operator ratio can be quantized via the OP RATIO button in order to lock it to more traditional and musical ratios or left free and wild for all types of FM madness. There is also an exponential FM input and attenuator as well as a SYNC input.

The CYCLE button, when engaged, will redraw the polygon from the cursor's last position. Engaging CYCLE is somewhat similar to the roll parameter but does produce different timbres than simply rotating the shape. Again the relative extreme or subtleness of the effect is dependent on the rest of the module's settings.

Last, but certainly not least—especially from a performance standpoint—the pitch setting can be "locked" by pressing all three buttons at once. This is a really nice feature to have, especially as the tactile immediacy of the module is so engaging, and it's great to be able to wiggle those sliders without worrying about bumping the module out of tune.

Since this is an instrument, it seems only natural to focus on how it sounds [amazing] but I have to admit that the visual feedback provided by this module is fantastically engaging and interesting to explore on its own. Of course, sight and sound in the Polygogo aren't mutually exclusive prospects and exploring the relationships between the shapes produced on screen with the waveforms that are outputted on an oscilloscope [and the consequent tones] is a rabbit hole that is a pleasure to fall down. I love FM synthesis for its ready ability to produce synth tones that can mutate for a split second from clean and pure—almost bell like tones—to gritty and harsh and back again, flickering between the serene and the insane. The Polygogo makes that kind of exploration and manic tone switching accessible and fun. Metallic and clangorous assaults are a fader slide away and it's easy to get to a place that can be almost too harsh, but it can and does yield beautiful and mellow sweet spots as well. Eye candy is one thing, but having the visual feedback really allows you to connect the relationships between what you see on screen and what you hear and can be an eye-opening shift in perspective. The Polygogo certainly goosed my tried-and-true sound design habits in a new direction and the immediate accessibility of the interface only adds to the experience. This is truly a hands-on module and even while modulating all the things, the Polygogo begs you to play it. For me, the siren song of its inviting controls and hypnotizing screen has ensured that it doesn't go untouched for long.

32HP +12V 110mA -12V 15mA

Price: $599

e-rm.de