Dusk Audio released Sunset Circuits v1.0.0 on July 27 — a free, open-source software synthesizer that bundles six distinct synth engines into a single plugin, running as VST3, CLAP, LV2, and (on macOS) AU across Windows, macOS, and Linux.
Six engines, not six presets
The six circuits are each modeled on a different classic synthesis approach rather than being palette-swapped variations of the same engine: Cosmos is a stable-tuned DCO polysynth; Oracle a self-oscillating analog five-voice with poly-mod routing; Mono an aggressive monophonic lead engine; Modular a patchable semi-modular design with built-in spring reverb; Prism FM a four-operator FM engine with eight algorithms; and Acid a screaming acid-bass box with its own step sequencer. That’s a genuinely wide net — DCO-style stability, analog self-oscillation, FM synthesis, and acid-sequenced bass are different enough synthesis families that most commercial synth bundles charge separately for instruments covering each one.
Around those six engines sit 54 factory presets, a searchable user preset browser, an eight-slot mod matrix, a host-locked arpeggiator and step sequencer, full MIDI implementation, and selectable 1x/2x/4x oversampling for cleaner high-frequency content at the cost of CPU.
The actual news is the licensing model
Free synth plugins aren’t rare, but most follow a familiar pattern: a demo with a watermark, a feature-locked “lite” version steering you toward a paid upgrade, or a free tier that requires an account and email signup. Dusk Audio’s stated position is blunt — all its plugins are 100% free: no trials, no feature locks, no accounts. Combined with the source code being open on GitHub, that’s a meaningfully different proposition from most of the “free plugin” category, and one worth watching to see whether Dusk Audio sustains a release cadence on that model or whether Sunset Circuits ends up a one-off.
For anyone building a sound-design or teaching setup where per-seat licensing costs add up fast, a genuinely unrestricted six-synth bundle is a real alternative to cobbling together six separate free plugins of inconsistent quality.