Chop Deck

A browser sampler and sequencer shaped like a late-90s hardware drum machine. The URL is the app: you load it and look down at the machine. Everything happens on the LCD and the front panel, the way it did on the 16-bit samplers that built a lot of records. Free, open source, no ads, no tracking, works offline.

Play it at chopdeck.com. Read the owner's manual.

• 99 sequences of 64 tracks at 96 ppq, real-time and step recording, timing correct with swing, note repeat, loop record, punch, undo, song mode
• 32-voice sampler: 24 programs, 4 DRUM slots, 64 notes per program, resonant low-pass filter, envelopes, velocity modulation, voice overlap and mute groups
• Sampling from a microphone or the machine itself, trim, loop, zone slicing to pads, time stretch, resampling, stereo/mono conversion
• Mixer with per-note level and pan, two multi-effect chains and two reverbs
• Web MIDI in and out (pads, MIDI tracks, clock, footswitches)
• A browser disk with folders, standard MIDI file and WAV import/export, mixdown to WAV, project bundles, autosave
• Optional, on chopdeck.com: an account that carries your project between computers, libraries of kits and public-domain samples, and beats you can publish, open on the machine and remix

Run it

npm install
npm run dev

The machine boots with a factory demo: a starter kit, a two-bar break already chopped onto program 2, two sequences and a song, so PLAY START makes a beat on the first visit (OTHER > INIT restores it). Open the printed URL in a Chromium browser (Web MIDI needs Chromium; everything else works in Firefox and Safari too). Hit a pad. Shift + a number key changes mode, exactly like the silkscreen on the keypad.

Run it anywhere, offline

npm run build

dist/ is the whole instrument as static files. Serve it from any web server, a USB stick, or npx serve dist. No account, no API, no network: the machine notices there is no site behind it and hides the site's links. Projects live in the browser; SAVE mode exports .CHOPDECK, .WAV and .MID files and LOAD brings them back.

Desktop app

The same build in a native window, for Windows, macOS and Linux, working entirely offline. Installers are attached to each GitHub release. docs/DESKTOP.md explains how it is put together (Tauri around dist/, one codebase) and how to cut a release.

Keyboard

Keys	Machine
Z X C V / A S D F / Q W E R / 1 2 3 4	pads 1-16 (bottom row first, like the panel)
Space, Shift+Space	PLAY / STOP, PLAY START
F1-F6	soft keys under the LCD
F7 F8 F9 F10	REC, OVER DUB, STOP, PLAY
Arrows	CURSOR
[ ] (Shift for x10)	DATA wheel
Enter, Esc/Backspace, Tab	ENTER, MAIN SCREEN, OPEN WINDOW
Numpad 0-9	numeric entry; Shift + top-row 0-9 = MODE
, . and ; '	BAR << >>, STEP < >
T, U, Delete, G	TAP TEMPO / NOTE REPEAT, UNDO SEQ, ERASE, GO TO

The same list lives on the machine under OTHER > HELP, and every control shows a tooltip on hover that links into the owner's manual at /manual/ (hold Alt and click a control to jump straight there). A first visit opens the QUICK START tour, a ten-step walk around the panel that ends with dropping in your own sounds, chopping them and recording; the same guide opens the manual.

Develop

npm run typecheck   # strict TypeScript, app and server
npm test            # Vitest: model, sequencer, DSP, every screen as text, the API on Miniflare
npm run test:e2e    # Playwright: boots the machine in Chromium, records a loop, loads a file, syncs, publishes
npm run build
npm run assets      # re-render public/og.png and the PNG icons from scripts/og/card.html

• design-system/ is the visual source of truth (tokens, component specs, the original concept).
• src/ds/ typed components ported from it.
• src/lcd/ the 48x8 character framebuffer and its renderer.
• src/kernel/ the firmware: modes, screens, fields, cursor, DATA wheel, numeric entry, windows.
• src/screens/ one file per mode; every screen is a pure function of machine state and is tested as text.
• src/model/ the machine data model, tick math, serialisation.
• src/seq/ transport and event operations.
• src/audio/ the sampler engine, DSP, effects, recorder, offline bounce.
• src/disk/ file formats (WAV, SMF, ZIP bundles), the IndexedDB drive, account sync, the libraries' client side.
• src/midi/ Web MIDI.
• server/ and functions/ the optional API: accounts, sync, kits, samples, beats, on Cloudflare Pages Functions with D1 and R2. docs/DEPLOY.md covers running it.

CONTRIBUTING.md has the rules that keep the code coherent and how to make a fork your own. ROADMAP.md is the plan and its status. docs/mpc2000xl-feature-inventory.md is the behavioural spec the screens follow.

Licence

MIT, see LICENSE. The name "Chop Deck", the wordmark and the logo are not part of the licence; forks are asked to pick their own. The machines that inspired this project and their names belong to their makers. Built by mcinnis.dev. If it earned a place on your desk, buy the maker a coffee.