Arroyo
A synthesizer you play at the level of the song. Not the note: the groove, the melody, the arrangement, the set, all under your hands at once. It has no grid. It makes noise on its own terms, and the work is wrangling that noise into something you love.
It runs in the browser, it's free, and it remembers how it was played.
What it is an instrument, not a tool
A tool bends to your exact wishes, and the fun of a tool is that it does what it's told. An instrument has ways. You learn them, you learn its secrets — there are settings in here that do things I didn't plan and can't fully explain, and they're the best things in it — and you bend toward it until the two of you meld. Getting good at it is the point. Nobody gets good at a tool.
So when the kit does something you didn't ask for, that's the instrument talking. Listen for a bar before you reach for the knob.
No grid the drummer's way
Every sequencer shows you sixteen boxes and asks you to fill some in. Arroyo doesn't have boxes. Underneath every voice is a field, a continuous terrain of probability around the pulse, computed fresh every bar. Turning a knob doesn't toggle steps; it reshapes the terrain, and the hits re-settle into it like water finding a channel. The research on why people move is built into the physics: syncopation held on the ridge where grooves live, timing that's consistently early or late rather than random, drops and builds a settled groove has earned.
Density is how much rain. Weight is how hard it hits. Swing is the lilt, Loose is the human part, Accent carves dynamics, Evolve lets patterns drift across phrases, Echo and Feedback feed a delay that does more work than you think. Nothing snaps, and everything you do is musical on the next bar.
Knobs and cables everything is a knob, and knobs can be wired
Every knob answers three gestures. Drag to play it. Double-tap to undo the last move. Triple-tap to ride: aim a ghost and the knob glides there over four, eight, sixteen, or thirty-two bars while your hands do something else. Or flick it: let go while it's moving fast and it coasts to a stop, a ride you start with a wrist instead of a plan.
Every knob also has a jack. Drag a cable from one knob to another and a move on the first becomes a move on the second — a macro, made in a second, with a pill on the wire to invert it. Every strip has a patch bay: the loaded module's own parameters as ports, so a macro or a modulator can reach inside ABUELA's filter. Cables into a bay are green; closed, they gather at the strip's dot.
Chords a progression is one knob
The progression knob turns chord changes into one detent per preset — off at the left, and any preset plays and loops from the next bar. The pitched strips resolve into each chord on their own: the melody finds the chord tones, the arp walks the new triad, the drive bass leans approach tones into every change because that's what a bass player would do, and a looped take transposes with the progression as if you'd sung it over every change. Press a number key and you get that degree on the next bar, by hand, when the room wants a lift the preset didn't plan. The key and scale live in the transport; change them mid-set and every strip follows on the downbeat.
Modulators hands that never get tired
An LFO and a looping envelope, each a small cluster of three knobs in a triangular box with one out jack. Wire that jack onto any knob — a macro, a strip knob, a port in a bay — and the modulator turns it, exactly as you would, around wherever you leave it. Your own setting stays underneath as a faint tick; grab a swinging knob and you move the centre of the swing. Sessions store your setting and the modulator, never the wobble, so a replay reruns the modulator from the clock and every wobble comes back in place. Double-tap the box to switch it off.
The looper every strip is an instrument you can play into
Make any strip the live input and your MIDI keyboard — or your voice, through the mic — plays through that strip's instrument and effects. Arm Rec and play: the first note is beat one, the take closes at one, two, four, or eight bars and loops at once. Then keep trying. Every pass you play in replaces the take; a pass you sit out keeps the last one. It usually takes a few goes to lock in with the kit, and this way nothing you fumbled survives. Press Keep and it's locked — and it's material now: the seven knobs refract it, Tens conforms it to the key, Evolve varies it, and you can keep it by name and load it into any strip in any song.
The song a map to play against, and a timeline you can wire
Pick a genre and you get a track's sections laid out in bars — intro, build, drop, break for EDM; a long ramp with plateaus for techno; verse and chorus for pop; one slow arc for ambient — each with the emotional energy a track in that style usually carries there, drawn as a dashed line. As you play, the playhead crosses it, the panel says build in 6, and a solid trace draws the intensity the machine is producing against the line.
Drop a cable from any knob onto the lane and you've pinned that knob to a level at that bar. Two pins and the knob follows the line between them: a whole song's Weight ramp in two drops, cascading through every cable that leaves it.
Cue and scenes how to change anything without the audience hearing you think
Double-tap the morph knob and the whole board tints blue: the room keeps hearing what it was hearing, and everything you touch now edits a second, silent deck — in your headphones, on its own MIDI channels. When it's ready, turn the knob and the room morphs from where it was to what you built. Load the next song onto the cue deck the same way, and the morph is the transition.
A scene is a song: every knob, every strip and its modules, the effect chains, the modulators and cables, and the board layout. The bank keeps them in the order you saved them — that's the set list.
Sessions the jam, kept
Everything Arroyo plays is a pure function of the scene, the knobs, the seed, and the bar number. So a session is the scene you started from and, bar by bar, what moved: knobs, rides, gestures, chords, takes, the modules' own settings, even where your hand was. A few kilobytes an hour, always on. Replay it and the knobs turn themselves. Grab any bars as a MIDI file, one track per strip, with every millisecond of microtiming. Record stems — one WAV per strip, plus the mix, plus the MIDI and the session, into one folder — and a good night is a finished track in Ableton.
And a session fits in a link. Send it, and whoever opens it watches the performance with the knobs turning and your hand drawn in — then presses × and the scene is theirs.
Viz the board becomes the show
The cursor becomes a drawn hand with a vapor trail. Knobs erupt when they turn — by your hand, a ride, a cable, a modulator, a replay. Pulses run down the cables. Each strip sends a ring out from behind itself when it fires. The room's light drifts with the music: warmer as Weight climbs, brighter as the hits come up, dimming into a drop. Put it on a projector behind you, or point a screen recorder at it. A shared session opens with it on.
The room every room lies about the mix
A one-off measurement at soundcheck: put the laptop where the audience will be, press measure, and an eight-second sweep goes out the master while the mic listens. What comes back is the PA and the room together. The panel fits a few cuts to the bumps that stick up — never boosts, never the bass unless you ask, because on a dance floor the bass is the reason people came — and keeps the measurement under the venue's name for next time. It also reads the room's decay, which is the reason to pull Echo back before you've played a note.
MIDI through and through every strip can drive anything
Arroyo's engine makes MIDI. The modules are one place that MIDI can go; a strip's channel is the other. Every pattern strip has a MIDI channel, and everything it plays — the hits, the echoes, the ghosts, every millisecond of microtiming — goes out on it as ordinary notes and CCs. Point an Ableton track at channel 10 and the kick strip is playing a Drum Rack. Point a DFAM at it and Arroyo is the DFAM's drummer. A strip can be a module, a hardware synth on the other end of a cable, or both at once, and the built-in sound is never in the way: it's a sketchpad you can turn off.
The same is true the other way. MIDI in plays the input strip and feeds the looper. CC knobs are ordinary MIDI knobs with a red ring, for whatever parameter your rig wants riding, and they ride, morph, and patch like every other knob. On a laptop it's Web MIDI directly; on an iPad it's a bridge on a Mac, or the desktop shell. And a session's MIDI export is a Standard MIDI File with a track per strip, so what you played to hardware tonight is what lands in the DAW tomorrow.
The voices each one has a temperament
Arroyo's sound is part of its character. The library is small and opinionated — a dozen voices at most, with names, not a catalogue — and every one runs in the browser as a Web Audio Module, loadable by URL into any host that speaks the standard. They ship inside the desktop app, and they're free.
ABUELA
The grandmother. Two oscillators, a four-pole ladder, an envelope that snaps, and a spring tank on the way out — the Moog family sound with its own drift. It's the default voice on the bass and lead strips, and it wanders on purpose: the drift knob is where the life is.
SICARIO
The slide. Every note is a destination the pitch travels to: twin saws and a sub, folded and driven into a mean ladder, with a growl LFO in the throat. Guttural by design. On the drone strip, above a certain Tension, it becomes a siren; that's one of the secrets.
CACHONDA
The kit's own voice: a tuned body with noise, a filter, and a snap, one note per hit, sized to the strip's role. Kick, clap, hat, tom out of one module, each strip carrying its own state.
MURALLA
The wall. Eight voices, each a stack of up to seven detuned saws with a square and a sub underneath, driven into an asymmetric fuzz on its own — every note distorts like its own amp — then a snapping filter, then the whole thing through an ensemble that spreads it across the room. Growly, dense, wide. It wants five fingers.
FANTASMA
The ghost. Eight pads; drop files on them, or pick from the studio pack. Each pad is a one-shot or sliced into pieces with a note per piece, so a chopped break sits beside your kicks and the field re-sequences both. Key mode pitches one sample across the keyboard for the melody strips. Start, end, loop, reverse, an envelope, a snapping filter, and a level that goes far enough past 100 to break. Your samples stay in your browser; scenes carry references.
LLORONA
The wandering reverb. A space whose walls don't stay put: the tail drifts, the width breathes, and it is never quite where you last heard it. On a lead it's air; on a drone it's the room the drone lives in.
ABRAZO
The embrace. A soft-knee stereo compressor with a sidechain highpass so the kick never squeezes the bass, peak or RMS ears, parallel mix, and a little warmth on the way out. Bass Hold on the drive bass; Drum Squeeze on a tom you want to hit harder; Glue on the master if you like what it does to a kit.
TECHO
The ceiling. A lookahead brickwall: it sees every peak before it arrives and has the gain down by the time it lands. Put it last on the master bus, ceiling at −0.3, and stop worrying. If you can hear it working on every bar, turn strips down instead.
Get it free, always
arroyo.strangefrequencies.fm — nothing to install. Chrome or Edge for MIDI to hardware; any browser for the modules. Works offline once you've opened it.
Open it in Safari and add it to the home screen. Full screen, a stage lock so nothing pans under your hands, stems to the share sheet, MIDI over Wi-Fi through a bridge on a Mac.
A desktop app — the same instrument with the voices built in, pinned to its own browser engine so nothing updates out from under a song. Releases.
The manual is inside the instrument, under ?. It was written to be read once and then forgotten, the way a good manual is.