Toaster

Toaster hears whatever is playing on your Mac or PC (Spotify, YouTube, anything) and writes it out as live Strudel code in front of you: named lines typed into a blank window and lighting up as they play. Around the code: every hit as a domino, a little world, a handheld rhythm game, or your webcam with effects you work with your hands. Toaster, as in Toaster Strudel.

Try it in your browser · Download for Windows or Mac

It finds the beat, the kick, clap and hats, the bass line, the chords and the key, and keeps rewriting the code as the song moves. It's a live reconstruction for show, not an exact transcription.

What it does

• Writes the song as code you can play. A line for each part, typed the way a live coder performs it (what you'll see in the code). It's real Strudel: press O and it opens in strudel.cc, ready to play; press X for the song so far as Strudel code and as a MIDI file.
• Your camera, worked with your hands. C turns it on. Frame something with your fingers and a window opens on it through one of 16 filters; make a circle with your hands and a portal opens, your own skull in X-ray first; ✌️ for the next theme, 👍 to record. K cuts you out over the visuals, or turns you to dots, voxels or glass.
• Visuals that move with the song. V for the background: thirteen little scenes, planets cut on the kick, liquid chrome, the cover fed through a pasta machine, the sound as a landscape and more; P for the dominoes, the song played as a rhythm game on a little handheld, or a punchcard.
• Little worlds. The scenery: thirteen scenes, from a lighthouse at sea to space to an eye that dives into its own pupil, every one answering the drop: hit D when it lands. Z hides the code and keeps just the visuals, for a live DJ set.

Get it

Windows 10 or 11, or macOS 13 or later. A webcam is optional.

Windows. Download Toaster-<version>-win-x64.zip from the Releases page, unzip it anywhere and double-click Toaster.exe. The first time, Windows may say "Windows protected your PC" (the app isn't signed): click More info, then Run anyway. It starts listening straight away; there's no prompt.

Mac. Download Toaster-<version>-mac-universal.zip from the Releases page (one app for Intel and Apple silicon), unzip it and drag Toaster into Applications. It isn't signed by Apple, so the first time the Mac won't open it: open System Settings → Privacy & Security, scroll down to Toaster and click Open Anyway. It asks to record system audio. Allow it. That's how Toaster hears what's playing; it doesn't record the screen, and the camera stays off until you press C.

Play some music: within a few seconds it finds the beat and starts typing. Press ? for the keys.

Updates. When a newer Toaster is out, it offers it a few seconds after it starts. On Windows, say yes and it downloads it, checks it against the checksum GitHub lists for it, closes, and opens again as the new version (your settings stay); on a Mac it opens the release's page. You can turn the check off in the help (?). The first time a new version opens, it shows what's new in it, each with its key, and the help keeps the latest additions at its top.

Keys

These are the keys as they come; every one can be changed in the help (?): click a key, press the one you want (a key that's taken swaps over). Esc, ? and F11 stay put. The help also has report a bug: Toaster writes a GitHub issue for you to read, edit and send yourself.

Key	Does
S	audio source: system audio, demo beat, file, input, radio
V	background, best first: scenes (a new one each song), worlds, chrome, spaghetti, spectrogram, cuts, fire, the code rain, off (each described under Backgrounds). The background button in the bar opens a picker with a picture of each, under five presets that set up a whole look in one click: live coding, visualizer, handheld, the Japan edition and for TikTok
A	the next one of whatever's showing (the footer says which). With the worlds on, their look: auto (film, and on each drop another look for 8 bars), night (as auto, but every world keeps a dark sky with its stars, so no cut lights the whole screen; with fewer flashes on, the worlds always have night skies), film, ASCII (the planet as text, each character in its own colour), thermal camera, and cells, the planet cut into cells of the worlds around it, turning over cell by cell into the next on each cut (after Days of Glitch's moving cells). A print look covers the planet, or the sky when the code sits over the planet. With chrome, A turns its collage off and on; with the spaghetti, its noodles: snakes (a card each time round, a few of its noodles dancing) or endless (the cover stuck on top, the machine never stopping, each noodle the cover again and again, spreading over the floor on the kick and dripping off it); with the spectrogram, it switches its colours between the rainbow and the theme's own; with the scenery, its scene: auto (a new one each song), the lake, the sea, the campfire, the snow, the city in the rain, the garden, the falls, Halloween, the sharks, the festival, the koi pond, space, the eye, and last auto again in the theme's two colours. With the handheld game on (P), A goes round the game's screens instead: Toaster's own (in the theme's colours), neon, an old LCD, and the Japan edition (Toaster's own in Japanese, in black and white, on a cream and red handheld after the Famicom: its screens, its cartridge and its power-on in katakana). Remembered
P	the code look, over whichever background is picked, in turn: dominoes (after mewtw0o's domino piano roll): every hit of the code stands as a domino that the playhead knocks over as it plays, landing on its beat and leaning on the one before when it's close, a held bass note a slab on legs that glows while the note holds and falls when it ends, a chord's notes one behind another; the handheld game (after mewtw0o's handheld rhythm game): the song played on a little two-screen handheld of our own, the kick, clap, hats and bass falling down their lanes onto their targets as they're heard, each judged by how near the real hit came (PERFECT, GREAT, GOOD), the combo and score climbing and a MISS when a part drops out; under it a 4 x 4 of pads, the drums and the twelve notes up from the song's key, lit as the bass and the chords play them, and now and then that screen turns into the code instead, its parts typing in as Toaster types them, a page at a time on the bar lines; its buttons go down with the drums, and a drop is FEVER, points doubled, for two bars (in the tall layout it fits in under the code, in place of the pitch roll). It powers on like an old handheld each time it comes on: its light, the screens flickering awake, the logo dropping in with a ding, a self-test of the song's parts, PRESS START. With no beat to play it stands by instead of going away: picked with nothing playing it says PLAY ANY SONG, with a song coming in READING while it finds the beat, and when the music stops CONTINUE? and a count, then GAME OVER; it powers on again when the music's back. On the pink theme it comes in a pink edition; then the punchcard blocks; then none. Remembered

The background, code look, card, theme, camera effect and drop-effect choices are remembered between launches, and so are the keys and the radio's address; the camera always starts off.

Backgrounds

V steps through them, best first: the scenery, worlds, chrome, the spaghetti, the spectrogram, cuts, fire, the code rain, off. A changes the scene or the look (see the keys above).

• Spectrogram is what Toaster hears, as a landscape, and what it makes of it: the sound rises out of a floor in glossy hills, the frequencies across it (the bass at the right, the highs far off to the left), a bar of time rolling toward you from the back, louder taller and further up a rainbow from orange through green and blue to violet and white (after the 3D spectrum analysers); a faint line crosses it on each beat and a bright one where the chord changes, named at its end, and each time Toaster recognises something a pin rides along with the code it became, bd on a kick, cp on a clap, hh on the hats, each bass note as the code writes it (e1, a3).

• Cuts gives each drum a scene of its own, cut to on its hits, each a view of the song in Toaster's look: the drum's word huge, its line of code magnified, its 16 steps as a punchcard, the spectrum falling in dots, the waveform, you or the cover in big dots, the tempo and key, the spectrum as text mirrored both ways like a kaleidoscope, a tunnel of rectangles flowing out (those two after rentalunit5's video-synth pieces).

• Fire is the old Doom fire in square pixels, lit by the song: it burns steady along the bottom, a little lower where the spectrum is quiet (the bass in the middle, the highs out at the sides); the song sets how high it reaches, the kick lifts it and the hats spit sparks. It burns low under the code, and smoulders while the song is quiet. When it comes on, and on every drop, it flares, leaping to twice its height and dying back (an idea from not.axel on Threads).

• The code rain is your code's own characters falling down the screen in streaks, faster as the song gets louder.

• Worlds is a film of planets, after Anthropic's Claude Opus 5.5 launch film: the kick on each bar's one cuts to another world on the same horizon (every other bar with fewer flashes), an extreme close-up of something (honey, agate, lace, a leaf, bread crust, plant cells, oil on water, a circuit board, the code itself) seen as a planet from low orbit, the foreground soft, gold dust in the air; when the kick drops out the film rests on a horizon at dawn till it's back.

• Chrome is a pool of liquid chrome seen from above with an oil-slick film on it: every kick drops a bead where it lands in the bar (so the rings spell out the kick pattern), claps strike lightning in the sky it mirrors, the bass swells it and each chord gives the film its own colours (real thin-film interference over the visible spectrum); every two bars a collage cuts into it: mosaic, dragged rows, a barcode, the liquid's contour lines, a dither, graph paper, and a panel with the song, artist, key and tempo.

• Spaghetti is the song's cover (or, without one, one of a dozen bundled public-domain pictures: Merian's banana, Seba's serpents, Brueghel's ark, Morris's Strawberry Thief and more) fed through a chrome pasta machine clamped to a kitchen table, on a tiled floor floating in the theme's colour: each time round the picture drops into the slot as a card, and from the next bar line the crank turns a beat at a time, lurching on the beat's hits, and out it comes underneath as spaghetti, each strand a column of the picture, flicked off as it leaves the rollers, falling in a low gravity, bouncing and piling up with the last two sheets', hopping on the kick, a few of them coming alive as snakes and dancing to the beat (a bounce on the beat, a dip on the kick, a pose on the snare, a roll up the body with each bass note, a jump on a drop), out among the others or in a ring round a soloist. With A, endless: the cover stuck on top and the machine never stopping, each noodle coming out without end, the cover again and again along it, the heap spreading over the floor on the kick and dripping off its edge.

What you'll see in the code

The code is typed the way a live coder performs it: a part that stops gets a _ in front of its name (Strudel's mute) and loses it when it comes back, a part never heard yet stays a comment, and a change lands on the next bar line, the way ctrl+enter on the downbeat does (the line flashes, and the rest of the code with it). Now and then a closing bracket gets left out: a red error shows, then the caret goes back to fix it.

• The filters sit on sliders, .lpf(slider(850, 100, 4000)) (Strudel draws a slider in the code for that); a thin track under each shows where the value is in its range, and when the music's filter moves, the number slides there instead of being retyped, like dragging the slider.
• A bass whose filter sweeps on the 8ths, triplets or 16ths (dubstep's wobble, riddim's pulse) gets Strudel's filter LFO, locked to the bar: .lpsync(8).lpdepth(3) for the 8ths, with some resonance and grit. The export writes it the same way.
• When the chords pump under the kick (sidechain, in most house and EDM), the kick gets .duck("2:3").duckdepth(.6) and the bass line and chords go on orbits 2 and 3, the way you'd set that up in Strudel. The depth follows how far they dip.
• The tempo line says // breakdown while the kick is out for a bar or more, and // drop for the first 4 bars after a drop.
• A line too long for the window (often, in the vertical layout) goes on over more rows, broken before a method call and indented, the way you'd break up Strudel by hand.
• Half-time music (dubstep, much of trap: the snare on 3 alone) is written the way its producer would: the bar starts two beats before the snare, the kick on 1 and the clap on 3, rather than the claps read as a 4/4 backbeat a beat off. A slow song heard at double its tempo (a ballad at 85 counted as 170, its backbeat landing once a bar) goes back to its own tempo, the snare on 2 and 4.

Saving things

• M records the window with its sound into Videos\Toaster on Windows, or Movies/Toaster on a Mac, as an MP4 ready for TikTok, Shorts and Reels. Switch to the vertical layout (L) first for a 1080 x 1920 video; it keeps everything clear of the edges Reels and TikTok trim on tall phones.
• J turns on drop clips: the first two drops of each song are saved as their own videos (the build-up and the drop) into that same folder.
• X exports the song so far into Music\Toaster on Windows, or Music/Toaster on a Mac: a MIDI file (drums, bass, chords and lead on their own tracks) and Strudel code, each phrase written once and played in order with arrange(). Paste it into strudel.cc and press ctrl+enter.

More on all three in docs/how-it-works.md. Filming Toaster for a video? docs/creators.md has the setup, the take, and how to carry on in Strudel.

For DJs and streamers

Toaster makes live visuals for a set: it follows the beat, and the scenes answer the drop.

1. Let it hear the set. On a Mac it hears everything the Mac plays, your DJ software too. With a mixer, pick its USB or line-in as the audio input (S).
2. Set the look. The Visualizer preset (the picker's first row, or Ctrl+K) shows the scenes with the code hidden; Z brings the code back (all but the beat, then all). V picks the background, T the theme.
3. Clear the frame. H hides the header, the footer and the player bar; F goes fullscreen.
4. The drop. Toaster fires it by itself when the kick comes back after a break of three seconds or more; press D the moment it lands to fire it yourself, and B to pick a drop effect.
5. Into OBS. Add Toaster's window as a source: on a Mac, macOS Screen Capture with the window method; on Windows, Window Capture with the capture method Windows 10 (1903 and up). Or press M to record the window with its sound.

Privacy

Everything Toaster hears and sees stays on your machine. The sound is worked out in the app, and the camera (off until you press C) is looked at by the system's own face detector (Windows' face detector, or the Mac's Vision framework) and by Google's MediaPipe, both running on your machine. Nothing is uploaded. It reaches the internet for three things only: GitHub, when it starts, to see whether there's a newer Toaster (turn that off in the help, under Updates), strudel.cc when you press O (your browser opens it with the code in the link), and the radio while it plays: its stream (from the server at the address you typed) and, for each song, the song's artist and title, sent to Apple's iTunes Search to find its cover (with what any web request carries: your IP address and the app's name and version); the cover is fetched from Apple's image server.

The site, toaster.locust.lol, works the same way: your audio never leaves your device. The site counts visits anonymously (Cloudflare Web Analytics, no cookies) and asks GitHub for the project's star count.

Good to know

• It does best with a steady beat. A song without clear drums can take 8 to 20 seconds to find one; tap Space on the beat to give it the tempo.
• The song's title (and its cover, for the ID card) come from the system's media controls (Windows' media controls, or the Mac's Now Playing), so any player that shows up there works: Spotify, browsers and the rest.
• The radio (S) plays an internet radio stream whose address you paste in; Toaster comes with no stations, but docs/radio-stations.md lists a few that publish theirs. In the app it reads the song titles the stream carries, and finds each song's cover in the iTunes Store (none if no song there matches); in a browser the radio is untitled. More in docs/how-it-works.md.
• For the finger frame, the portals and the hand signs, keep your hands a little inside the camera's picture.
• On a touch screen (an iPad, say), ☰ in the header opens every key as a button, each showing what it's set to.
• What it can and can't hear yet: the end of docs/how-it-works.md.

Build it yourself

With Node.js (it's built with Node 24):

npm install
npm start          # run it
npm run dev        # run it with a debugging port (9333) for tools/cdp.mjs and tools/checks.js
npm run package    # build for the OS you're on: dist/Toaster-win32-x64, or dist/Toaster-darwin-universal

On a Mac, npm start compiles the Swift helpers (now playing, and faces) the first time, with Xcode's command line tools. npm run package:win and npm run package:mac build the other OS's app; the Mac app has to be built on a Mac. Each release's Mac app is built on GitHub's Macs (.github/workflows/mac.yml), signed ad hoc.

How it works inside, and the test songs it's checked against: docs/how-it-works.md.

Built with Toaster

• golden by Jon Soini: a free iPhone player for Apple Music in Toaster's look, with its code view, ID cards and themes. Toaster's dynamic theme (the colours of the song's cover) and its library (G) are after golden's.
• Internet radio by Jeffrey Li (#6, #7): paste a stream's address and Toaster plays it and writes it out. He has also built a background of his own on top of Toaster.
• A 3D-printed handheld by Clemens (@tokyo_impressions), printed from the game's model.

Made something with Toaster? Show it in Discussions, or see CONTRIBUTING.md to build on it.

Credits and license

Toaster is MIT licensed (LICENSE). It uses Google's MediaPipe (Apache 2.0) for the camera; THIRD-PARTY-NOTICES.txt lists everything it uses and the artists whose looks it's after. The code it writes is Strudel. Toaster is an independent project, not made by or affiliated with the Strudel project.

If Toaster made you smile, a star helps more people find it.