Physical Audio releases Tetrad Synthesizer Plugin (VST3/AU/AAX)

Physical Audio has announced the availability of a new synthesizer plugin, Tetrad. The synth was developed in collaboration with experimental musician Gadi Sassoon, and has an unfamiliar set of features for creating and processing its sound, including four physically modelled slashed plates with transducers attached.

How Tetrad Works

Tetrad's signal flow starts from its Quad Oscillators, which can generate four-note chords, four related partials, custom microtonal signals, or more traditional four-oscillator sounds. The signal is then sent through a 4x4 Matrix Mixer, allowing for blending of different voices into four buses.

From here, the signal is sent through three unusual processors.

The Quad AM module takes the four input buses and modulates their amplitude. Using controls such as Phase Offset, the four signals can be separated in time for rhythmic effects, pseudo-arpeggios and pseudo-sequences.

The Quad Granulator is a module created especially to handle Tetrad's four-part signals. As is common in any granulator, this one can change grain size and shape, pitchshift, add jitter to the window position and use feedback, but with the four-voice architecture, it can also set a different Grain Size and Pitch per input bus.

The Quad Plates module sees the signal sent into four physically modelled plates, each slashed to give a different mode of vibration. These plates are parts of collaborator Gadi Sassoon's 'sculpture-based synth' as heard on his album Modes of Vibration. In Tetrad, the effect of the plates' metal cuts, their decay, and preamp drive can be set. Decay and Drive can also be set per plate in the 'Quad' view of the module.

Being at the end of the signal chain, the four plates can be moved in the stereo field on a virtual sound stage before output Trim and Limiter finalize the output.

Tetrad can also accept sidechain input to use its Quad AM, Quad Granulator and Quad Plates modules as processors, or to stack instances of Tetrad for feedback effects.

YouTube.com/watch?v=qfKiQW7kFk8

Tetrad Features

• 115 factory presets at launch.

• 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 'amount', Preamp Drive globally; or Drive and Decay per plate.

• Sidechain input allows external signals to be sent through the plugin after the sound generation stage.

• Quad Output lets Tetrad's four output buses exit the plugin on separate channels.

• MPE-compatible with a glide range of +/- 48 semitones.

• Comprehensive Modulation Matrix with 40 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.

Technical Specifications

• VST3, Audio Units, AAX plugin for macOS 10.13+.
• VST3, AAX plugin for Windows 11+.
• Sample Rates: 44.1kHz, 48kHz, 88kHz, 96kHz.

Pricing & Availability

Tetrad is available now for the introductory price of $59 (then $99) until 28th July 2025. It is available as a synthesizer plugin for Windows and macOS in VST3, AU and AAX formats.