Tetrad

Tetrad is like no other synth you've ever used. Developed in collaboration with composer and transmedia artist Gadi Sassoon, the plugin takes four voices, routes them in combination through a Quad AM processor that works like a pseudo-sequencer, a specifically tailored Granulator, and four physically modelled slashed plate resonators.

Inspired by Gadi's sculpture-based synth installation, as heard on the album Modes of Vibration, Tetrad was originally devised as a complement to the slashed plates and sound generators of the experimental setup, but has grown into a plugin instrument that puts the capabilities of the whole installation into a single piece of software in a DAW.

Oscillators

It starts with the oscillators, which give a choice of five modes, each with four voices or oscillators per note (hence the name Tetrad). In the oscillators' Global view, you can change the main oscillator waveshape, and apply frequency modulation with control over the FM Depth and FM Rate. An amplitude envelope (ADSR) sculpts the source tone that outputs from the oscillators, but this tone will go through much more processing on its way through the synth.

Get to know the five sound generator types. Basic builds a sound using four layered oscillators, in a similar way to traditional synthesizers. Chord offers 36 diatonic tetrad chords to choose from, and Inversion and Drop Voicings to rearrange them. Modal allows specific scales so that tetrads are always in key, but also adds the Inversion and Drop selections. Micro lets you tune four oscillators away from the fundamental frequency (from cents up to an octave). Flex mode generates harmonically related partials above, below or either side of the fundamental frequency.

4x4 Matrix Mixer

Blend the four input channels into four output channels, with simple control over Bleed, or custom control over the 4x4 gain matrix.

Quad AM

Put aside everything you ever learnt about synths. This four-voice amplitude modulation module has a Phase Offset macro for the four voices, resulting in pseudo-arpeggiator effects. Exact phase values can be set in the module's 'Quad' view. Amplitude modulation has Depth, Shape and Rate, which works well into the audio range.

Quad Granulator

Here the signal is split into grains that are replayed in different ways. You can affect the grains' window shape, Size, Pitch, and change the Feedback of the granulator. HOP Rand applies variation to the window's position?, and grains can be synced and reversed. From the Quad display, Grain Size and Pitch can be set individually per voice channel. The Quad Granulator isn't to be confused with a granular synthesizer, but is a granular processor design specifically for Tetrad's internal signals.

Plate Resonators

In the physical instrument, four suspended plates are used as resonators. These plates are scarred with slashes at different angles, and have strategically placed transducers to take advantage of each one's specific modes of vibration. In Tetrad these Suspended Plate Resonators are physically modelled and the four voice channels sent through them. The plates can be panned and levelled in the virtual sound stage.

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