Physical Audio Tetrad 1.0.2 macOS U2B

Tetrad is a hybrid instrument based on physical modelling and granular synthesis. A unique quad bus signal chain feeds 4 modelled plates alongside a full modulation matrix, creating a soundscape that rewards experimentation.

Like No Other Synth
Tetrad is like no other synth you’ve ever used. Developed in collaboration with composer and transmedia artist Gadi Sassoon, the plugin takes four oscillators, routes them in combination through a Quad AM processor that works like a pseudo-sequencer, a specifically tailored Granulator, and four physically modelled 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 installation into a single piece of software in a DAW.

How Tetrad Works
It starts with the oscillators, which give a choice of five modes, each with four oscillators per voice (hence the name Tetrad). In the Macro view, you can change the main oscillator waveshape, and apply frequency modulation. Oscillators can be tuned in various ways according to the chosen mode, from basic intervals to diatonic inversions. An ADSR provides initial amplitude shaping before heading down to the mixer. There is also a Sidechain audio option, bypassing the oscillators and allowing any signal to be used.

A 4×4 Matrix Mixer blends the four inputs onto four busses. Next is Quad Amplitude Modulation with Depth, Shape and Rate, which works well into the audio range, and Phase set individually per bus. In Tetrad’s Quad Granulator, 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. Finally this feeds the Plates through a preamp with overdrive.

To Infinity: Modulation Matrix and MPE
Tetrad encourages you to think in a different way about creating sound, and its modulation matrix widens the scope even further. Here, you can route sources to ten destinations from a choice of over 45. Each routing has an amount to set its depth.

Sources include eight LFOs, MIDI values and MPE dimensions. Envelopes include the synth’s main ADSR as well as some envelope-following signals, which are derived from the AM and Granulator levels, making these sources self-modulatable. Each source has a visual indicator of its value to help understand its effects on the signal.

MPE Velocity, Slide, Pressure and Glide are available as modulation sources for the full MPE experience. In MPE mode, pitchbend and glide are available continuously across the full range of MIDI notes.

Features:
– Over 100 presets to get started immediately.
– Generate voices through Basic, Chords and Modal chords, Free and Flex modes. Plus ADSR envelope, FM Frequency and FM Depth for all oscillator types.
– Quad AM module to ‘pseudo-sequence’ or gently modulation voices, with control over phase Shape, Depth, Gain and Rate (up to 250Hz), plus Phase Displacement per voice.
– Quad Granulator mangles the four voices into new textures individually or all together. Grain Size, Feedback, Rate (up to 50Hz), or individual Grain Size and Pitch per voice.
– Plate Resonators that can be driven and positioned graphically on the virtual sound stage. Set Decay, Metal Cuts, Preamp Drive globally; or Drive and Decay per plate.
– Comprehensive Modulation Matrix with over ## destinations, eight LFOs and three envelope-following sources, plus MIDI and MPE parameter sources.
– Three filters (LP/BP/HP) to curtail and sculpt effects from audio-rate modulation distortion and extreme granulation artefacts.

Compatibility: macOS 10.13 or later • Apple Silicon or Intel Core processor
Homepage https://physicalaudio.co.uk/products/tetrad/