No install. You supply your own Williams sound ROMs (read in your browser, never uploaded), then explore the algorithms at slow motion. Works in Chrome and Firefox.
The Williams Sound Explorer and Designer (WSED) is a browser tool for the arcade sound effects of Defender (1980), Stargate / Defender II (1981), and Robotron 2084 (1982). Every sound on those cabinets is a tiny program running on a Motorola 6802 that streams bytes to an 8-bit DAC. WSED emulates that sound CPU and makes the algorithms visible (oscilloscope, spectrogram, DAC byte-tape, per-engine state, RAM heatmap) and audible at human-scale time — from 1× down to single-instruction stepping — and lets you design your own sounds (Design mode). Drive it by mouse or keyboard — Space fires, 1–4 set speed, ←/→ scrub or single-step, G cycles game, and ? lists every shortcut.
Defender's descending SAW at ¼× — the oscilloscope, live 6800 disassembly, DAC byte-tape, and routine swimlane update in lockstep.
⚠️ You must supply your own ROMs. This project does not include the Williams sound ROMs — they are © Williams Electronics. On first run the app asks you to upload them; the files stay in your browser (IndexedDB) and are never sent anywhere. See Supplying ROMs.
cd explorer
npm install
npm run dev # → http://localhost:5173On first run an onboarding screen asks for the Williams sound ROM of each game. Drop a file on a slot — the app validates it (size + 6802 vectors + a SHA-1 allowlist) and stores it locally. The explorer works with as few as one ROM; games without one stay locked until you add them.
The sound ROM for each game is a small chip image (2 KB for Defender/Stargate, 4 KB for Robotron). Obtain them from a source you're entitled to use:
- a MAME romset you are licensed to use (the sound ROM is inside the game's zip — the app verifies it and tells you which game it is), or
- a dump from your own board, or
- build them from source (see below).
Nothing is uploaded; ROMs live only in your browser's IndexedDB. Use Remove on a slot to delete one.
The assemble-from-source toolchain is included, but the Williams sound source is not (it is copyrighted). To rebuild the ROMs yourself:
- Obtain the Williams sound source and place it at
research/williams-soundroms/(VSNDRM1.SRC… for Defender/Stargate/Robotron). - Install the
vasm6800 assembler — seedocs/pipeline/vasm_install_notes.md. - Run
tools/build_roms.sh→ producesresearch/roms/*_sound.bin. cd explorer && npm run dev:romscopies them into the gitignoredpublic/roms/so the app auto-loads them and skips onboarding.
| Path | What |
|---|---|
explorer/ |
The TypeScript app (Vite + plain TS + canvas). 6802 emulator, PIA, synth, AudioWorklet pipeline, all the visualizations. |
tools/ |
Assembler toolchain (build_roms.sh, preprocessor) + data generators (glossary, label map, explainer cards, zero-page map). |
docs/ |
Curated reference: hardware model, the 8 synthesis primitives, per-game command catalogues, pedagogical design, architecture. Start at docs/README.md. |
MANUAL.md |
Explorer manual — 12 tutorials + interface tour. |
MANUAL_DESIGNER.md |
Designer manual — build your own custom sound ROM (Design mode). |
Beyond exploring, the app has a separate Design mode (the Explore | Design toggle in the header) for forking a game's sound bank: opens with the game's editable sounds pre-loaded, edit any VARI, GWAVE, LFSR, FNOISE, or RADIO sound's parameter record with sliders (and a wavetable canvas for GWAVE/RADIO), audition + A/B, and save as a JSON recipe (no ROM bytes) — or download a runnable custom .bin to load in MAME / a real cabinet, and upload it back to keep editing. Hit ▶ Open in Explore to push your custom ROM into Explore's live worklet — pause/step/scrub on your own sound, with every Explore visualisation pointed at it. See MANUAL_DESIGNER.md.
Most tools for these sounds either play them (emulators) or document them (disassemblies); a couple let you tweak them. WSED sets out to do all of it — emulate the real hardware, make every layer visible at human-scale time, and let you design new sounds — across all three games.
MAME emulates the whole cabinet (main CPU, video, and the sound board) for faithful play and preservation — it's the gold standard for accuracy, and WSED uses MAME's output as a golden reference for its regression tests. But MAME is a black box for understanding: you hear the result, you can't watch the 6802 execute, see the DAC byte stream, tell which ROM routine is running, or inspect an engine's internal state — and there's no slow-motion, no single-instruction stepping, and no way to edit a sound. WSED runs the same sound CPU but surfaces all of that and slows it to a crawl. → docs/pipeline/reference_audio_plan.md
The closest peer: Defender Sound Studio, a browser tool by Daniel Lopez (msarnoff) that lets you pick a Defender sound, tweak its parameters, and hear it, with an oscilloscope/FFT and JSON preset import/export. WSED deliberately reuses two of its good ideas — labelled parameter controls with tooltips, and JSON import/export — but differs in five ways:
By design:
- Real ROM, not a re-implementation. The Studio is a hand-written JavaScript port of each routine; WSED runs the actual ROM bytes on a cycle-accurate 6802 emulator, so it's bit-faithful and any valid ROM works unchanged.
- Three games, not one. Defender only, vs. WSED's Defender + Stargate + Robotron.
- Explore + Design, not just tweak. WSED has a separate Explore mode (DAC byte-tape, routine swimlane, LFSR/engine state, RAM heatmap, spectrogram, scrubber, single-step) — and the Designer's Open in Explore + ↓ .bin push your custom ROM into Explore's live pipeline or MAME respectively. The Studio is play-and-tweak only.
.binround-trip. WSED's Designer downloads a runnable custom ROM you can load in MAME or burn to EPROM, and uploads it back to keep editing. The Studio's saved artefact is a JSON preset that stays in the browser.
Current state (editor coverage):
The Studio's 9 UI tabs include 6 editable tabs covering 5 distinct engines in WSED's taxonomy (it splits LFSR across multiple tabs WSED would group together). WSED now edits all 5 (VARI + GWAVE + LFSR + FNOISE + RADIO) — per-engine parity with the Studio on Defender — but across all three games, running the actual ROMs rather than a hand-port across one. SCREAM and HYPER are un-editable in both tools — they have no preset record in the ROM.
→ docs/design/sound_studio_reference.md; the full feature-by-feature table is in MANUAL_DESIGNER.md.
Computer Archeology, ZEN Instruments, and Nameless Algorithm offer excellent static documentation — annotated source listings and prose explaining how the routines work. WSED stands on their shoulders (and links them), but makes the same code audible, animated at human-scale time, and editable rather than read-only. → links in docs/README.md
cd explorer
npm test # Vitest
npm run typecheck # strict tsc --noEmit
npm run build # production bundle → explorer/dist (no ROM bytes)MIT — see LICENSE. The MIT license covers the explorer app, the build tooling, and the documentation. It does not cover the Williams sound ROMs (© Williams Electronics, not included), nor the third-party vasm assembler and npm dependencies, which keep their own licenses.
The names Defender, Stargate, Robotron 2084, and Williams are used descriptively to identify the games whose sound code is analyzed here; no affiliation or endorsement is implied.