The Ensoniq SQ-80 was an 8-voice multitimbral wavetable synthesizer with analog filters and a multi-track sequencer, released in 1988. In 2006, Siegfried Kullmann wrote SQ8L, a free emulation of it — and then, for years, nothing happened.
SQ8L was written in Delphi and never updated beyond 32-bit, Windows-only. On any modern system it was unrunnable. It is now back, as a free, open-source revival running as VST2, VST3, AU, CLAP and LV2 on macOS (native Apple Silicon and Intel), Linux and Windows.
A preset demo of the original SQ8L — the sound the revival preserves.
How they did it, and why that is unusual
The code was never released as open source. So the revival team did not port the source. They rebuilt the plugin from the original binary, using AI as part of the process, specifically so that people could keep playing it.
That approach deserves to be stated plainly because it is the crux of the project, and it is a genuinely hard kind of work. Reconstructing a functioning synthesizer from a compiled 32-bit Windows DLL means recovering the DSP from machine code: the oscillator loop, the wavetable interpolation, the filter topology and its coefficient calculations, the envelope shapes, the modulation routing. Delphi’s own runtime and object layout sit in the way. And the test for success is not “it compiles” but “it sounds identical,” which is a far stricter bar.
They claim to have met it. At 8 voices, the sound is bit-exact.
This is also, bluntly, the only route that existed. Kullmann’s plugin was free but closed; without source, the options were a clean-room reimplementation from the hardware — which is what Arturia did commercially with SQ80 V for its V Collection — or reconstruction from the artefact. Twenty years of people’s patches and project files depend on this plugin’s exact behaviour, not on a different emulation of the same synth, and only one of those routes preserves them.
What changed
Polyphony from 8 to 64 voices, adjustable with a new VOICES parameter. The important detail: with 8 voices the sound is bit-exact, and behaviour changes only where the original would have stolen a voice.
That is the correct way to add polyphony to a vintage emulation. Voice stealing is not a limitation sitting outside the sound — it is part of the sound, audible as notes cutting off in dense passages, and plenty of parts were written around it. Making the original count the default and the expansion opt-in means old projects open unchanged.
The rest:
- Native OS controls for popup menus, message boxes, file pickers and the WRITE/MIDI-port dialogs
- A few editor additions, including the VOICES parameter on the EMU page
- Editor window scaling from 100% to 300% — the fix that matters most in practice, since a 2006 plugin UI on a modern display is otherwise unreadable
- Liberation Sans with anti-aliasing for the status bar and program name, a free font metrically compatible with Arial
- Two original bugs that could not be reproduced were made safe
And the honest limitations:
- SEND/REQ to a hardware SQ-80 or ESQ-1 over MIDI ports is not connected yet. SysEx import and export through files works.
- Sample rates below 44.1 kHz are not supported, as in the original.
- The current build is beta.
The hardware SysEx gap is the one to watch if you own the real thing — the appeal of a software SQ-80 that can swap patches directly with an SQ-80 or an ESQ-1 is considerable, and file-based SysEx is a workaround rather than the feature.
Why the SQ-80 is worth this effort
It sits in a specific and under-appreciated place. The SQ-80’s oscillators read wavetables — not the smooth analog shapes of its contemporaries, but short digital waves, many of them derived from sampled and transient material — and then run them through analog filters. That combination gives it a brittle, slightly gritty character that neither a pure analog polysynth nor a later all-digital workstation produces.
It is the same hybrid lineage as the ESQ-1 before it, and it is the reason the SQ-80 keeps resurfacing in music made decades after Ensoniq folded.
Twenty years of a free plugin being the way most people could hear that, followed by twenty years of it not running, followed by this: a reasonable outcome.