User guide

How to play bender, once the board is in front of you.

Playing the keyboard

The on-screen board draws three octaves starting at C3, fewer on a narrow window or phone. z/x shift the whole board two octaves either way. The sixteen keys under your typing hand carry their letter, printed the way the toy printed note names on its own keys.

Hold latches every key you touch until you press it again. Alt-click pins down a single key on its own, for a drone under both hands. A key that loses its release — the window loses focus, a controller unplugs mid-press — releases itself, so the note doesn’t ring forever.

Keys light for whatever is actually playing them: your hand in the accent colour, the toy playing itself (the ROM tune, the auto bass-chord, the trigger patch) in amber. A note fades from the light as it fades from the mix, and a note cut short by a brownout goes dark early. A note played past either end of the drawn board marks that end instead.

Tone taps the divider chain at 1/2, 1/4, 1/8 or 1/16 pulse width. The narrower taps thin the sound by nulling different harmonics, uncorrected, same as the original chips. Near the top of the keyboard’s range a counter can’t strike a pulse that narrow, so the narrow settings widen back toward a plain square.

The melody memory

Rec on the deck, or record on the piano roll, arms recording — even with the chip silent. Every key you press after that, on-screen, on the letter keys, or from a controller, writes to the step the chip is standing on.

What you record isn’t a separate sequencer: it’s the 19th entry on Tune, one past the 18 ROM songs, and the chip treats it the same as any of them — Memory rate sets its speed, the auto bass-chord plays under it, the clock bend and a brownout affect it the same way, and Struck by can clock it from the drum machine instead of the crystal.

The piano roll draws that memory: one row per pitch, one column per step. Click a cell to place a note, drag to draw a run, click again to remove it, shift-click to hold the previous step’s note. A held note draws as one bar across its steps. Two octaves show at a time, with arrows to move the window. The memory is 32 steps and keeps its own length, so a four-step phrase loops eight times against a sixteen-step drum pattern.

A step is one of 64 codes: 62 pitches (a little over five octaves) plus rest and hold. The octave switch can move the keyboard further than those codes reach; a note at the far end wraps to the nearest octave that fits. The accompaniment takes the melody’s lowest note as its tonic and checks for a flat third to pick major or minor.

The memory is undo-tracked like the drum pattern — random rolls, mutate and morph never touch it, it rides in the shared link, and every note or hold you play is its own step in the undo history.

Auto bass-chord

Auto bass-chord is the accompaniment section: bass on the beat, a chord stab on the offbeat, the bass alternating root and fifth. It runs off the melody’s own step clock, reads its chord from the tune currently playing, and runs on the same divider and rail as everything else — starving the chip or dragging its clock takes the backing band down with the tune.

The arpeggiator

Arpeggio takes the keys you’re holding and plays them one at a time: up, down, up-down, random, or as played (the order your fingers went down). Hold a chord, or throw the hold switch and let go — latched keys arpeggiate the same as held ones.

Arp rate is notes a second; Arp range is how many octaves the figure climbs before repeating. Neither is its own clock — the arpeggiator runs off the chip’s divider, so Clock, a pot on the timing pin and a flat rail all drag the figure with the tune. Kit sync does not reach it.

The figure goes out on the gate line like any other note, so it plays the FM chip too wherever that jumper is soldered on, and Keys fire kit turns it into a drum pattern.

Kit sync

Kit sync brings the drum machine’s step clock to the toy’s timing chain, so the tune counts off the kit’s tempo instead of its own crystal. Pick how much of a beat one step of the tune is worth: sixteenths, eighths, or quarters. It reaches the melody, both memory lanes, and the auto bass-chord — not the arpeggiator, which keeps its own rate knob.

It replaces the rate the song was written at, nothing else: Clock, a pot on the timing pin, Crystal drift and a flat rail still move a locked toy the same as a free one. It’s a wire on the timing pin, not a phase detector — both machines hang off the one divider, so a sag lands on both sides at once.

Off is the crystal, and off is the default. lock, beside Clock, is the older way to the same place: it sets the crystal to the nearest speed at which this song’s steps divide into the kit’s, once, then holds nothing.

The key lock

Key lock closes a key off the scale onto the one under it. Pick a scale (major, minor, dorian, mixolydian, either pentatonic, blues, whole tone) and a Key, and everything played into the board comes out in that key: both keybeds, a MIDI controller, the arpeggiator, and the trigger patch’s any step. It moves a note by a semitone or two, never an octave.

It sits on the key line: the demo songs and your melody memory always play in whatever key they were written in. Off is the default.

The drum machine

The kit is a sixteen-step grid. Eight voices — kick, snare, hat, clap, tom, cowbell, open hat, cymbal — each get a row of steps, with an accent row underneath. Ten factory patterns sit as buttons above the grid, each an editable starting point.

Tempo carries a tap button: press it in time and the kit takes the speed off your hand. The same button sits on both delay times and the patch bay’s oscillator.

Swing holds every offbeat step back and gives the next step less time. Tune and Decay move the whole kit; Ring is the one to reach for after those — the kick, tom and snare body are resonant networks, and winding Ring past nine tenths latches them into notes that ring until you wind it back. See Bends for what Ring, Trigger pulse, Snappy, Accent sag, Bit depth, Ladder, Voice slot and Overflow do to the kit’s cheap-DAC quirks. Voice slot ties the kit together: one converter serves eight voices, so a step that stacks the kit comes out coarser than the same voice alone.

Kit switches the box between two of them. Nothing here is a sample, so the sampled kit is this kit sampled by itself: on its way up the machine strikes all eight voices through the ordinary circuits and files them as twelve-bit slabs, and a hit plays the slab back instead of ringing the network. Pattern, accent, trigger floor, retrigger, choke and every knife on the bus work as before. What goes quiet is what shapes a voice, since the ROM was cut with those knobs where they were: Snappy, Noise bias, Metal, Bank spread, Squarer bias, Cymbal tone and Ring reach nothing, and the cross-patch bridges pins a recording does not have. In their place, ROM clock is how fast the slabs are read: cut at 26,040 Hz, read at half that they land an octave down and half as bright, which is the trick every record made on one of those boxes is built from. Decay becomes truncation under 1×.

Four voices are one part: the cowbell, both hats and the cymbal come off a single bank of six square oscillators. Bank spread widens the bank, detuning the cowbell and roughening the hats together. Metal blends between that bank and the noise transistor the hat used to be made of; Cymbal tone slides the cymbal between a crash and a splash. The two hats share a cap — writing a hat step under a ringing open hat cuts it short, the way a foot does — and Choke moves that resistor to any pair of voices.

Press a step and drag across the grid to draw a run. Each row has its own length: shift-click a step to loop the row back from there, with a badge showing where it ends (press the badge to give it all sixteen back). A five-step hat against a sixteen-step kick is polymeter — the two line up again only every eighty steps.

Click a step past lit and it wires through the kit’s dice instead: drawn as a ring with a dot, it fires as often as Chance says. A third click turns it off. Chance at zero silences those steps; Chance at max makes them ordinary. An accent is a weight on whatever step already fires, so the accent row carries no dice.

Roll, Vary, Turnaround, Shift, and Half/Double rewrite the grid without touching tempo or tone: a new pattern, a couple of small changes, a fill over the end of the bar, every row moved one step later (shift-click to move back), and the bar stretched or compressed.

The echo row under the accents throws hits into the tape delay. Throw lights the bar’s last snare. The first throw on a silent delay brings it up with Bus send at zero, so only the throws echo.

A row’s name is also a preview button. The kit plays on the number row too: 1 is the kick through 8 the cymbal. The toy drum machine’s rubber pads do the same, with lamps that follow the step counter and its own ▶/rec switches. Record arms the kit to write from what you play — needs the kit running to land on a step.

Playing the FM chip

The FM chip has no sequencer of its own; its key input is wired onto the toy keyboard’s gate line, so it plays whatever the toy strikes. Struck by can wire a kit voice onto that line too.

One computer keyboard, three keybeds: a s d f and the octave keys z/x play whichever bed has computer keyboard plays this bed ticked, in the drawer behind the three bars on its deck, and the letters are printed on that bed’s keys so you can see where they went. Turning it off on a bed hands the letters back to the toy’s, which is the one bed always on the page. Every bed takes the mouse either way, and a MIDI controller plays the toy’s unless you point it somewhere else or split the keybed — see MIDI.

Voice picks one of eight patches, Brightness sets how much modulator reaches the carrier, Feedback sets how much modulator feeds back into itself. A key held under your hand stays on for as long as you hold it; anything else that triggers the chip — the demo song, a drum hit, a trigger line — sends only an edge, so Note length decides when it stops. Four voices (e.piano, bell, bass, marimba) decay on their own regardless of key state; the other four wait for release.

Level, Brightness and Feedback run past the chip’s normal range — a red tick marks it, and the readout turns red past it. Level goes to ×4; past 1 on Brightness and past 7 on Feedback a booster takes over from the register, multiplying modulation and feedback further. Drive pushes the four voices into the output stage, up to 36 dB, squaring notes into fuzz.

Vibrato switches on the die’s one LFO — no rate or depth register, just two bits wiring the operators to a wobble that’s been running since the board came up. tremolo takes about a decibel off the level, vibrato moves pitch about seven cents, both does both. Tremolo reads quieter than expected because a modulator moving up and down moves brightness the opposite way from the carrier’s level — wind Brightness down and it’s obvious.

Rhythm re-taps the top two channels onto a ROM kit instead of the keyboard: a bass drum, and a snare and hi-hat fed by the chip’s one noise source, a shift register. It costs two of the four voices, the same two an effect wants. Noise blob solders that shift register onto the sine table with the rhythm bank switched over — a touch is dirt on the note, wound across it gates the carrier by the register instead.

Mod ratio, Car ratio and Mod decay shape the patch further; see Bends for what a fault actually does at the register level. The patch bay reaches every knob that matters, knife included: FM cut depth, FM noise blob, FM bright — and FM bright is worth trying first, since the processor only re-sends a patch when a knob moves, so a wire there writes the register every block instead of four times a note.

Playing the home keyboard

The third machine on the rail is the eight-bit sampling keyboard, and it is the only thing on the board that makes pads, strings, choirs and bells. There is no oscillator in it: a ROM holds one short recording of each voice — an attack and then a loop — and a counter walks that ROM at whatever rate the note asks for. Bring Level up and its bed appears under the toy’s, in grey plastic, with the same toy gate jumper the FM chip has: soldered out of the box, so the demo song plays it.

Voice picks the recording and Envelope picks one of the four buttons down the side of the case — piano falls away whether or not you are holding the key, organ holds, pad swells, chime rings. Release is the one capacitor the buttons do not choose, and it is also what decides how long a strike off the toy’s gate or the kit’s trigger lines lasts, since neither of those has a hand on it. Chord memory puts a whole voicing under one key, which fills all four voices doing it — press a second key and the first is stolen, exactly as one of these always did.

Two knobs are the part rather than the sound. The ROM was cut at 9.9 kHz with nothing interpolating on the way out, so every voice comes back with its own images sitting over it, and Tone is the two-pole reconstruction filter deciding how much of that you hear: up is the grit, down is the underwater version the same chip sounds like through a plastic speaker. ROM clock drags the counter itself, which is the classic bend on a keyboard like this — pitch and aliasing move together, because on this part they are the same thing.

sampled is the voice the machine is famous for. It plays whatever you dropped on the sampler across the keys, out of a second and a half of memory at the ROM’s own rate, with the reel’s own loop markers as its loop — so a file on the page and a chord button is a vaporwave part. Turn the sampler’s own fader down and the keyed copy is the only one you hear. With nothing threaded it is silent.

The knife reaches both of the chip’s buses. Address line is the counter’s own wires: every word that comes back is a real word from the wrong place, so a voice folds onto its own first half or reads every sample twice. Data line is the famous one — the top wire held high and the bottom half of every wave folds up onto the top of it. The named cuts under that heading are the six worth hearing first.

The talking pet

The talking pet is a furry toy wired onto the keyboard’s batteries. Raise Level and it says hello. What it says depends on its mood:

• asleep — snores now and then; any sound or kit hit wakes it.
• awake — greets you and chats; twenty seconds of quiet makes it sleepy, a long stretch awake makes it hungry.
• chatty — after a kit hit; laughs and sings.
• hungry — asks for food until the next kit hit.
• scared — after a loud sound or a burst of hits.
• sleepy — yawns, then sleeps; a low supply keeps it here.

It hears the mic and the board’s own output, ignoring the output while it talks. Chatter sets how often it talks unprompted and how long it stays awake in quiet. Pitch moves the voice alone; Clock moves pitch, formants and speed together. Motor is the eye-and-ear motor, which loads the shared supply when it turns. The knife, Frame hold and K bits are in Bends.

While Level is above zero the pet appears under the toy keyboard and drum machine. Its ears swing and eyelids close while the motor turns, its beak opens with speech, a bubble shows the phrase, and a caption names its mood. Clicking it tickles it: a sleeping pet wakes, an awake one gets chatty, a quick run of clicks scares it.

The trigger patch

The keyboard and drum machine share a power rail by accident; the trigger patch is what you wire between them on purpose.

Kit fires keys bridges a drum hit onto the keyboard’s gate: the note played is its own setting — the one already standing, the next step of the ROM tune, a random step, or a tone from the current chord. Next step is the one to try first, since it clocks the whole board, bass and chord stabs included, off one drum hit.

Keys fire kit is the wire back: every note the chip plays also fires a drum voice, pattern running or not. The step option hands it to the grid instead, so a key fires whatever column the sequencer sits on.

Bridge both directions and the two machines play each other — a rattle at the audio block rate, held in check by the safety tail.

Two more wires land on the FM chip, the only way anything reaches it. Toy gate is the factory jumper off the keyboard’s gate line; cut it and the chip stops following the keyboard. Struck by clips the kit’s trigger lines onto the same input, one voice per pentatonic step, turning a drum pattern into a riff. Every wire here, and the shared rail, can also be bent — see Bends.

Presets and rolls

Click a preset to load the whole board. Drag it sideways and it morphs only part of the way there, under your finger; drag back and it retraces. Random rolls, mutate, and drift never touch the demo song, the pattern, or the output/mic/sample levels.

A roll moves only a handful of controls, and any control that counts in beats (delay time, glitch slice, drum retrigger) lands on a division of the beat. A control with red ticks has a normal range — rolls, mutate and drift stay inside it unless you’ve already set it past. Wreck it, slam and on the edge use the whole track.

Every stage’s panel has its own roll and reset; the signal path map’s control count, pressed, does the same reset without opening the panel.

Whole-board rolls sit above the presets: rewire shuffles the bend order without retuning, one bend clears the slots to one and rolls it hard, wreck it pushes feedback, supply and bit depth all at once (the safety tail holds it), slam drives one to three controls to an extreme, on the edge drives two opposing controls to opposite extremes, let it age turns all five ageing controls up together, patch solders two or three wires from a moving source onto a stage that’s actually running, and cascade solders one wire onto another wire’s own depth.

Dub builds a dub desk around what is playing: a dark tape echo in time, a filter in its loop, a spring and a crackling filter.

Every control a wire can land on carries a + mod button beside its readout: the press solders the first spare LFO wire onto that control and folds the wire out under the row, tagged with what’s driving it and how fast (∿ LFO 1.0Hz). Press the chip to fold it back, × unplug to remove it — the next + mod restores the same patch. It’s an ordinary bay wire throughout, saved and shared like the rest.

Hunt tries six boards, plays each a second and a half, and keeps whichever rides closest to the limiter without burying it. None of the candidates it passed through land in the undo history — the whole hunt is a single step.

Hunt a tail plays six dub boards and keeps whichever rings on most between the kit’s hits. After either hunt, the numbered row picks any of the six.

Drift is mutate on a timer: roughly every fifteen seconds the board sets off toward a new nearby setting, so the sound never cuts and never quite arrives. One ctrl+z restores the board from before it started.

While it drifts, ⟲ 10s stops and goes back to where it was ten seconds ago.

Share copies the current board into the page’s URL.

Demo songs

The ROM bank holds 18 tunes: four factory demos, eight public-domain pieces (Für Elise, Ode to Joy, Rondo alla Turca, William Tell, and others), and six slower ones in minor and modal keys. Once you’ve played something into the melody memory, it’s the 19th entry on the same selector.

Throws

The hold row under the run buttons pushes the board somewhere while you hold it and springs back when you let go: spin (c), dive (v), brake (b), crash (n), drop (m) and crush (,). A throw never lands in the link or the undo walk.

Playback and recording

play demo song and play drums are independent run switches. space toggles both at once and restores whatever was actually running before.

Record wav captures the actual audio output as a 16-bit stereo wav file — different from the keyboard’s Rec and the drum machine’s Record, which capture what you played rather than what comes out of the speakers.

⟲ last 30s saves the last half minute of output even if nothing was recording, and ⟲ → reel puts it on the sampler instead.

Varispeed

Varispeed, in the Output panel, is the deck the whole instrument is printed to. Everything else on the board — the tape machine and the limiter included — is upstream of it, so turning it down slows the pitch, the tempo, every envelope and every delay and reverb tail together, and nothing upstream knows. Motor weight beside it is how long the platter takes to get where the knob is: wind it up and dragging Varispeed to the stop is a tape stop that runs down, and letting it back up is a spin-up.

A wire from the patch bay lands on deck speed like any other lane, so one LFO wobbles the whole board. The mic is resampled on the way in, so a voice through a slowed board still comes out at the pitch you sang it. A take, master and stems both, is what the deck played.

Stems

The selector beside it sets what a take comes back as. Master only is one file. Master + stems adds one wav per source that had anything on it — toy keyboard, drums, FM chip, chaos oscillator, noise, sampler, pet — named bender-<stamp>-toy.wav, -drums, -fm, -chaos, -noise, -sampler, -pet, beside bender-<stamp>-master.wav.

A stem is the dry source, taken where it sums into the mix bus — before the bus drive, bends, pedals, brownout, tape and limiter, all of which apply only to the sum. Stems won’t add up to the master in a DAW; the master is the instrument, the stems are what went into it. The mic and the feedback return aren’t stems — the mic lands on the bus, the return feeds the desk back into itself — both are in the master only.

Stems are mono: five of the six sources put the same sample on both channels, and noise takes the middle of its two streams. A stem take stops at two minutes (a master take gets ten) — seven tracks of 48 kHz float run about 1.5 MB per second held in the tab. There’s no zip, so stopping a stem take fires up to seven downloads at once; your browser may ask permission for multiple files.

The link is the board

The address bar carries the whole board — every control off stock, the drum pattern, the melody — in the #, with no server involved. It comes out short by default:

https://cmdcolin.github.io/bender/app/#p=AJYBL1p-AgDABwCQAQDoBwF4

The long form spells the same board out, and the app reads and writes both:

https://cmdcolin.github.io/bender/app/#set=chipLevel:0.75,drumLevel:0.45,echoMode:1,echoMs:480,echoFb:0.72,echoToneHz:5000,echoLevel:0.6

The long form is four times the characters, which is why the bar carries the short one, but it’s what lets you program a board by hand: a control name from features.md, a colon, a number, commas between.

#set=chipStarve:0.8,dlyFb:0.6,drumKick:33825

Anything left out is stock, anything out of range is pulled back, and an unknown name is dropped. A bar already carrying #set= keeps carrying it; type a bare #set= to switch a tab over. Every preset link in features.md is written this way.

Signing in and saved voices

A voice is a whole board under a name. Three things save one, all saving the same thing: save in the panel’s row of verbs, ctrl+S (⌘S on a Mac), and the saved popover’s name box.

A press saves under the name the popover is already showing — the preset the board is standing on, or the voice you last saved or recalled. A name already in the list overwrites that voice in place.

Pressing save with nobody signed in opens why sign in?. Sign in from there and the board you were looking at saves under the name you gave it; a name your account already holds gets a number appended (dying toy 2).

Each row in the list: press the name to recall it (shift+click to overwrite it with the current board); ↗ opens it whole and at once; ⧉ copies a link to it, playable signed out; × deletes it.

The list lives on your Google account, so a voice named on the laptop is there on the phone, and clearing site data doesn’t lose it. sign in becomes your account photo once you’re in; press it to sign out. Nothing else in bender needs an account — presets, rolls, MIDI, recording and every link work signed out. The privacy page lists what the account holds.

Signed in, the app also mirrors the board you have open onto your account; the home page offers it back under Continue where you left off. A recording on the sampler and the mic don’t travel with it. Opening the app, a demo, or a shared link doesn’t touch the mirror until you change something.

The home page lists your voices, newest first. Copy link, Rename (refuses a name another voice already has), and Delete (asks once) sit under each card.