The first module from Glasgow-based maker Instruo, Troika appears fairly simple at first glance, with 3 nearly identical oscillators contained in a single module. However, a closer look reveals some interesting depth to this device, making it a powerful tool for classic subtractive sounds or complex tone shaping.

Troika has three individual oscillators, each with independent coarse and fine tuning controls ranging from LFO to supersonic frequencies, 1 volt per octave cv inputs, sync cv inputs and linear fm inputs with attenuators. Each oscillator has a dedicated output port, as well as a level knob to control the signal level to the summed mix out. The 1 volt per octave control for Oscillators 2 and 3 can be linked to the oscillator 1 1v/oct cv control using the by flipping the switches along the left side of the module into the down position, for key tracking and unison performance.

The waveform sections on each voice are each unique, despite the similar appearance. The first oscillator includes the 4 basic wave shapes, crossfading between either sine and triangle shapes, or square and saw. The second channel contains the same shapes, however this time the shapes are switched, crossfading instead between sine and square, or triangle and saw. The third oscillator crossfades between sine and saw, or switches to a pulse wave with control over the pulsewidth via knob or cv.

Troika really comes to life when you start patching the outputs back to the inputs. Since the oscillators can dip down to low frequencies, we can use them as modulation sources for the linear FM inputs on the other channels. In the video, I use oscillator 3 as a modulation oscillator, turning the level knob down so the low frequencies do not pass out of the mix out. The dedicated channel 3 output is not attenuated by the level knob, so I route it to the channel 1 linear FM input, slightly adjusting the FM knob to create some vibrato. As the oscillator 3 frequency and the linear FM knob rise, more sideband frequencies are generated, creating gorgeous atonal results.

The sync inputs are also incredibly useful for shaping complex harmonic content in Troika. Routing one dedicated oscillator output to another channel sync input, forces the synced oscillator to restart it’s wave cycle whenever the leading oscillator wave cycle rises in voltage. This causes the synced oscillator to generate musical harmonics, while retaining a similar pitch to the leading oscillator.

Troika can create incredibly complex tones when you begin to combine these many functions or incorporate a few external modules, from Moog-style layering to additive klangs. What are you using to generate complex tones in your system?

Troika From Instruo Eurorack Triple Oscillator

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