Retromulator

A standalone app and DAW plugin (AAX / VST3 / AU) that emulates classic hardware synthesizers, samplers, and keyboards by running their original firmware on cycle-accurate CPU and DSP emulators.

56k emulator cores require their original ROM firmware to run (not included). ROMs are loaded from the application support folder at runtime. The SC-88 family needs a full image set per board, kept together in its own folder and identified by content. The Matrix-1000 EPROMs are only used, when present, to write ROM banks 2 to 9. The microQ can run with an embedded fallback ROM. The Akai S1000, AY-3-8910, DX7, Matrix-1000, Nord Lead 1/2/2X (Nordic 1 and 2), OpenB3, OpenWurli, OPL3, and Tracker cores are ROM-free. The files each core needs, with their sizes and hashes, are listed under ROM Files.

The Akai S1000 sampler loads SF2, SFZ, ZBP, and ZBB sample banks, as well as Akai ISO/BIN/CUE disk images, via the SFZero MIT-licensed engine with 8-point sinc interpolation, extended SFZ/SF2 opcode support, auto-slice drum mapping, CC20 global tuning, and discoDSP Bliss sampler format.

The AY-3-8910 / YM2149 emulates the 3-channel PSG used in the ZX Spectrum, Amstrad CPC, MSX, and Atari ST using the Ayumi engine, with a voice layer re-implementing the Ym2149Synth firmware: soft volume and pitch envelopes, glide, vibrato, detune, noise delay, and transpose. Voices are controlled via CC 1–11 and patches are stored in a user bank.

The Commodore 64 SID emulates the MOS 6581 / 8580 chip using the reSID engine with 3-voice polyphony, oldest-voice stealing, and a full 50 Hz macro playback engine (wavetable, pulsetable, filtertable, speedtable). It loads GoatTracker .sng banks and .ins standalone instruments, with live MIDI control via CC 1 (vibrato depth), CC 22 (pitch bend range, 1–48 semitones), CC 64 (sustain pedal), CC 71 (resonance), CC 74 (cutoff), and CC 75 (pulse width).

The Hammond B3 (OpenB3) is the setBfree tonewheel organ and Leslie engine by way of OpenB3, with upper, lower and pedal drawbars, percussion, vibrato and chorus, overdrive, three Leslie cabinets with convolution cabinet bodies, a plate reverb, a keyboard split and .fxp presets in Factory and User banks.

The Nord Lead 1 (Nordic) is a clean-room C++ reimplementation of the 1995 Nord Lead 1 DSP program, bit exact to the original and checked against a real unit, so it needs no ROM. It has 48 voices, unison, morph, the arpeggiator and all four slots A-D, each on its own MIDI channel, with its own editor below the rack. Nord Lead 2 programs can be imported and exported. Nordic is hosted from ROM/Nordic.vst3 and ships only with commercial builds.

The Nord Lead 2/2X (Nordic 2) is a clean-room C++ reimplementation of the Nord Lead 2 DSP program, bit exact to the original and checked against a real unit, so it needs no ROM. It has 64 voices, unison, morph, the arpeggiator and all four slots A-D, each on its own MIDI channel, with its own editor below the rack. It reads Nord Lead 1, Nord Lead 2 and N2X banks. Nordic 2 is hosted from ROM/Nordic2.vst3 and ships only with commercial builds.

The MiniD is an analog three-oscillator monosynth by discoDSP, voiced from measurements of analog hardware: oscillator shapes and drift, a transistor ladder filter with a HI (high-pass) mode, filter and loudness contours, noise and VCA. It has Poly, Unison with 2, 4 or 8 voices, Double voicing, its own panel below the rack and a Factory bank of 49 presets. MiniD is hosted from ROM/MiniD.vst3 and ships only with commercial builds.

The Oberheim Matrix-1000 runs on a clean-room controller that needs no firmware, driving CEM3396 voice models with BLEP oscillators and 2x oversampling on six boards that wake up as more notes play, for 36 voices. ROM banks 2 to 9 are written once into .syx files with the factory names when the original EPROM images are installed. Every patch parameter is exposed to the host and mapped to a MIDI CC, and both LFOs can follow the host tempo, MIDI clock or a SysEx tempo.

The Roland SC-88 family emulates the SC-88, SC-88VL, SC-88Pro, SC-8850 and SC-55mkII GS sound modules, running each board's own firmware on an H8/500 or SH-2 core with the Roland tone generator, effects and filter chips. Tone and drum kit names are read from the board ROM, and the GS parameter map is exposed to the host: per-part programs, variation banks (CC0), tone maps (CC32) and the rhythm part assignment. A standard MIDI file, or a playlist of them, can be played through the board and rendered offline to WAV or MP3 320, from the plugin or from the command line.

The Tracker core plays XM and MOD modules through the Fasttracker 2 replayer, and S3M and IT through the Schism Tracker player with Nuked OPL3 for Adlib instruments. The module owns the transport, driven by MIDI notes: play, stop, and step through a playlist, which can be shuffled or stop at its end. A song ends after five seconds of silence. Folders and .m3u playlists are expanded, the song tempo can follow the host, and a module or a whole playlist renders offline to WAV or MP3 320 with 512 tap sinc interpolation.

The Wurlitzer 200A (OpenWurli) is a physical model of the Wurlitzer 200A electric piano with 64-voice polyphony, tremolo, speaker character modeling, velocity curves, and 2x oversampling.

The Yamaha OPL3 emulates the YMF262 FM synthesis chip (18 channels, 4-operator) using the Nuked OPL3 engine. It loads SBI patch files with bank navigation via folder hierarchy, pitch bend, and voice stealing.

The standalone app opens modules, .m3u playlists and .mid files handed over by the OS (double click, Open With, or a drop on the dock icon) and switches to the matching core.

The plugin has a MIDI output that can pass on what the emulated core sends (SysEx dumps, parameter changes), switched on with midiOutCoreOutput="1" in settings.xml.

A core can also run without its sound engine, as an editor for the real synth, with editorOnly_<core name>="1" in settings.xml (spaces in the name become underscores).

Required ROM files per hardware core. The filename is not checked: any file of the correct size and content is accepted.

ROMs go in the ROM folder inside the Retromulator data folder, and the Roland SC-88 family sets (SC-55mkII, SC-88, SC-88VL, SC-88Pro, SC-8850) in its 88emu folder:

• macOS: ~/Library/Application Support/discoDSP/Retromulator/
• Windows: Documents\discoDSP\Retromulator\
• Linux: ~/Documents/discoDSP/Retromulator/

• chiaccona — VDX7, cycle-accurate Yamaha DX7 emulation (HD6303R CPU, EGS, OPS), GPL v3
• Dag Lem — reSID, cycle-accurate MOS 6581 / 8580 SID emulation, GPL v2
• discoDSP — SFZero v3.0.0, 8-point sinc interpolation, Bliss format, extended opcode support, MIT license; synthLib device adapters, bank and patch handling, offline WAV / MP3 render and host parameter pool, Oberheim Matrix-1000 emulation, GPL v3; Nordic Nord Lead 1/2 DSP reimplementation, proprietary, not in this repository
• Dominic Mazzoni — libresample, sinc resampling, BSD 3-Clause / LGPL dual
• dsp56300 — DSP56300 emulator, Virus TI / microQ / XT / Roland JP-8000 (JE-8086) / SC-88 family engines, GPL v3
• Jean-Marc Valin — Speex arbitrary-rate resampler, BSD 3-Clause
• Joshua Price — OpenWurli Wurlitzer 200A physical model
• Lasse Öörni / Cadaver — GoatTracker .sng / .ins format reference, GPL v2
• Leo Olivers — SFZero JUCE module port
• Michele Perrone — OpenB3 Hammond B3 and Leslie, AGPL v3, based on setBfree by Robin Gareus, GPL v2+
• Nuke.YKT — Nuked OPL3, cycle-accurate YMF262 emulation, LGPL v2.1
• Olav Sorensen — Fasttracker 2 clone, XM / MOD replayer, BSD 3-Clause
• Peter Sovietov — Ayumi, AY-3-8910 / YM2149 emulation, MIT license
• Schism Tracker contributors — Schism Tracker, S3M / IT player, GPL v2
• Steve Folta — original SFZero SFZ/SF2 sample player, MIT license
• Timothy Lamb — Ym2149Synth, voice engine and soft envelope firmware, GPL v3

JUCE integration, UI, AAX/AU/VST3 plumbing is developed separately.

The emulation engine source code in this repository is licensed under the GNU General Public License v3.0 (see LICENSE.txt). Bundled third-party components keep their own licenses: