Physical Audio’s latest synth draws on real-world sculpture to offer a distinctive digital sound palette
UK-based software developer Physical Audio has released its fourth synthesizer plugin, Tetrad, which is now available in VST3, AU, and AAX formats. Tetrad expands on Physical Audio’s focus on real-time physical modelling by integrating a range of signal processing techniques with a conceptual approach inspired by physical sculpture.
Tetrad’s development draws directly from the work of experimental musician and artist Gadi Sassoon. His original installation, known as the “Sculpture-based Synth,” used slashed metal plates and a custom Max/MSP setup to explore sound design via physical interaction. Tetrad is positioned as the digital twin of this artwork, transforming its tactile roots into a plugin format.
Feature-rich synthesis without samples
At the core of Tetrad is a four-voice engine with several layers of signal manipulation. Each oscillator supports Basic, Chords, Modal chords, Free, and Flex modes and includes FM synthesis controls. These voices pass through three unique processing modules: Quad AM, Quad Granulator, and Quad Plate Resonators – offering deep control at both macro and per-voice levels.
The Quad AM module introduces phase-based modulation with control over shape, depth, gain, and rate up to 250Hz. The Granulator can be applied globally or per voice, introducing parameters like grain size, feedback, and pitch variation. Plate Resonators simulate slashed metal plates, allowing users to place and excite them graphically on a virtual stage, adjusting decay, drive, and tonal shaping.
The plugin supports MPE (MIDI Polyphonic Expression), with a glide range of ±48 semitones, and includes a sidechain input and quad-channel output. A modulation matrix offers more than 40 destinations with 8 LFOs and MIDI/MPE source routing, reinforcing the synth’s experimental design ethos.
Key Features of Tetrad
- 115 presets included
- Voice generation via Basic, Chords, Modal Chords, Free, and Flex modes
- ADSR envelope, FM Frequency, and FM Depth available for all oscillator types
- Quad AM (Amplitude Modulation) module with control over Shape, Depth, Gain, Rate (up to 250 Hz), and Phase Displacement per voice
- Quad Granulator module for mangling voices, with parameters like Grain Size, Feedback, Rate (up to 50 Hz), and individual Grain Size and Pitch per voice
- Plate Resonators with graphical positioning and controls for Decay, Metal Cuts amount, and Preamp Drive; supports per-plate Drive and Decay
- MPE-compatible with a glide range of ±48 semitones
- Modulation Matrix with over 40 destinations, 8 LFOs, and both MIDI and MPE sources
- Three filters (Low Pass, Band Pass, High Pass) for shaping and sculpting the sound
- Sidechain input and Quad output support
Tetrad arrives at a time when physical modelling and MPE integration are increasingly valued by electronic musicians seeking nuanced control and expressive possibilities. As DAWs and controllers become more capable of high-resolution modulation and real-time interaction, plugins like Tetrad align with a growing interest in moving beyond traditional sample-based synthesis.
Physical Audio, known for using pure numerical modelling of acoustic systems, continues this trajectory with Tetrad. By avoiding samples or impulse responses, the company maintains a commitment to real-time computation, enabling sonic results that retain a physical feel without hardware dependency.
Availability and pricing
Tetrad is priced at $59 / £47 / €47+VAT as an introductory offer, with a regular price of $99 / £79 / €80+VAT set to take effect from July 28, 2025.
Find out more on Physical Audio website.
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