Keys 🎹

An accessibility-first, mouse-only playable MIDI keyboard as a VST3 (and standalone app). Keys makes no sound of its own: you click the on-screen piano and it sends MIDI to whatever instrument sits downstream, in your DAW or over a virtual port. Built for creators who work entirely with a mouse, including users with motor disabilities: every control is a single click, a drag, or a scroll. No keyboard and no modifier keys. Right-click is only ever an accelerator, with two exceptions Owen asked for: Lock, in a chord card's menu, and releasing one note out of a chord the Sustain pedal is holding. Neither has a left-click twin.

Because it is a plugin, your setup travels with the song: keyboard size, scale-lock, octave, channel, velocity, sustain and latch, the Humanize settings, the both arpeggiators down to their step lanes and their twelve slots each, which sections you had folded away and which you had pulled out into windows of their own (down to where each window sat, the chord generator's included), this instance's colour, the eight knob CC assignments, and your captured chord pads all save into the DAW project and come back when you reopen it. And it drops straight onto a track, with no loopMIDI to configure.

Built with JUCE 8 and CMake, on the shared okstudio-juce-kit.

Two products build from this repo:

• Keys: the keyboard itself, driving a downstream instrument over MIDI.
• Keys Host: the keyboard plus one hosted instrument VST3 in a single plugin on a single track. Pick the synth from an in-window browser that files every installed VST3 into a collapsible folder per publisher; its GUI opens in its own floating window; its complete state (including MIDI Learn mappings) saves inside the DAW project. The 8 knobs auto-bind to the synth's likeliest parameters (cutoff, resonance, envelope, and so on) by name. See docs/ABLETON_LIVE.md for how it fits Live.

The hex-grid sibling, Hex Host, moved out to its own repo: ../Hex.

One view, no tabs, and four sections stacked down the window: Controls (the dropdowns and the eight knobs under them), the arpeggiator, the chord pads, and the playing surface. Every section folds away so the window can be squeezed small: click the chevron at the left of its bar, or the caption beside it. That left end is the target, and a hairline shows where it stops, so a click that misses a bar control does nothing rather than hiding the thing you were reaching for. Every section also detaches into a resizable window of its own. An open section's bar is a ruled band with a tick of accent; a folded one goes flat and dim, so the shape of the window reads before you have read a caption.

Playing it

Gesture	Result
Click a key	Play that note
Click and drag	Glide across keys (monophonic)
Sustain on, click several keys	Notes keep sounding after release, like a pedal; with the pedal down a glide leaves a trail, and clicking a ringing key plays it again. All Off stops everything
Latch on, click several keys	Each click holds that key, and clicking it again releases it — the way to build a chord note by note, or take one apart
Right-click a key (optional)	Toggle a hold on that one note, the Octavium accelerator. A key this keyboard is already holding lets go, so a walk along a ringing chord takes it apart a note at a time without lifting Sustain. Any other key latches on, and a plain left click releases that
Knob row	Eight rotary CC knobs, the bottom row of the Controls section, each with a one-click reassign button (see Controls below)
Chord pads	Build a chord, drag the live card onto a pad to capture it, then press the pad beat-pad style to play it (Sustain holds it). Drag a pad back onto the card to bring its notes up for editing
Fill / Regen / Generator	Three chips at the right of the Pads bar. Fill writes chords to the empty pads and never overwrites; Regen re-rolls the pads that already have one, except the locked ones; Generator opens the rest of it in a window of its own
All Off	Stop every note on every channel gently: per-note offs plus CC123, so notes end through their release envelopes instead of being choked

No gesture beyond a click, a drag, or a scroll is ever required. Sustain is an on-screen toggle, not a modifier key, on purpose. Right-click opens the card menus on the chord pads and the arp slots, and toggles a hold on a key; only Lock and releasing a pedal-held note live nowhere else.

Controls

Control	What it does
Size	25 / 49 / 61 / 73 / 76 / 88 keys
Root + Scale	The key and scale used by Scale Lock
Scale Lock	Snap every played note to the nearest note in (Root, Scale) — you can't hit a wrong note. Out-of-scale keys are dimmed.
Octave	Transpose the whole keyboard by -5..+5 octaves
Velocity	A range. Humanize off plays its midpoint, on takes a random value inside it. Drag an end to resize, the middle to move the whole band, or collapse it for a fixed velocity
MIDI Ch	Output channel, 1–16
Voices	Polyphony limit: Off (unlimited) or 1–8 notes, stealing the oldest
Mod / Pitch wheels	Left of the keyboard: Mod sends CC1 and holds; Pitch bends and glides back to centre. Both move by relative drag, never jumping to a click
Sustain	Hold notes after release (pedal). A repeated key is a repeated strike, so you can play over a chord that is still ringing
Latch	Click to hold a key, click again to release it. Sustain's twin, and the difference between them is exactly that second click
Humanize	Draw each note's velocity at random from the Velocity range, so repeats and chords don't sound machine-perfect
Knobs	Eight rotary CC knobs; the label under each opens a one-click reassign menu. They are the bottom row of the Controls section, and the Knobs chip on that bar folds just that row
Chord pads	Their own section, and the only chord cards in Keys. Capture chords to sixteen pads a page and press beat-pad style to play (Sustain holds); Exclusive chokes the last chord, Strum rakes a chord's notes Up / Down / Random over a time drawn from its range. Four numbered buttons on the Pads bar pick the page. Every card shows the chord's name with its notes (octave numbers included) on a line underneath, in the same two rows of eight; Big, which used to swap that for four rows of four with a mini keyboard on each, went on 2026-07-31 once the note list fit on the small card too
MIDI in	Play a hardware keyboard through Keys and its keys light up on screen, with the live card naming the chord. The stream passes through untouched
BPM	Tempo the arpeggiators run at when there is no transport to follow — always in the standalone, and whenever the host is stopped. A playing host wins, and an arp rate set in Hz follows neither
Arp	Its own section, and the one Keys opens showing. Two arpeggiators, A and B, each with its own rate, shape, pattern, twelve slots, chord and chain — so a polyrhythm is one plugin, not two. The bar carries a switch per line, Hold off, All Off (both lines off and everything let go, in one click) and Light keys (lights the keyboard for what the arp is playing — display only), all of which survive the section being folded shut. Inside, the All view puts both lines on one screen as rows: rate with its Sync/Hz switch and its Dot / Trip / Anchor, shape, seven knobs (Oct, Gate, Chance, Swing, Offset, Vol, Human), the chord it holds and its Chain, over the tempo and Launch Quantize they share. Oct is a transpose, centred at zero, so a line sits an octave under the other rather than only ever stacking upward. The A and B tabs beside it go deep on one line: the full control band, the ten-lane step editor and twelve launchable slots, each holding a pattern, a chord and a rate that one click installs. Hand a line a chord by clicking a card with that line on, or by dragging the card onto a slot, a tab or a line's row. Handing a chord to a line that is off is silent and not lost — the line holds it and starts the moment you switch it on. Twelve shapes (including Chord, which plays the whole held chord every step) plus Pattern; Distance stacks the chord by scale degrees rather than fixed intervals; Chain plays a line's twelve slots as a progression, each for the bars its card shows
Rate	A dial in the arp's control band, with a Sync / Hz switch beside it. Sync detents through eleven tempo-synced divisions, 16 bars down to 1/64; Hz free-runs from 0.031 to 32 Hz, which is exactly the span those divisions cover at 120 bpm, and never reads the transport. Dot, Trip and Anchor grey out in Hz, since there is no beat left to subdivide or bar to pin to. A pair of steppers beside the dial walks every value one at a time, so nothing here needs a drag
Quantize	In the macro view, shared by both lines. Off fires a chord the instant you click it; anything else (1/16 up to 2 bars) holds the click until the next boundary, so a card can only ever land on the grid. Ableton's Quantization, for the arp. It never delays the keys you play
Hold off	On the Arp bar. Lets go of the chord every line is holding and stops every Chain — one button on purpose, since a per-line release would leave the other two droning behind a folded bar. Greyed out when there is nothing to let go of. Clicking the lit pad restrikes the chord instead, so this is the way to stop a hold outright
Fill / Regen / Generator	The chord generator, at the right of the Pads bar, with Key, Mode and Scale Compliance as combo boxes beside them. Generator opens a window holding every setting it has, plus a 4x4 tray for auditioning candidate chords, with its own Fill / Regen / Clear, before they touch a pad. See below
Theme	Colour this instance, so you can tell it from Keys on your other tracks
Detach	On every open section bar: puts that section in a resizable window of its own. Re-dock from inside the window, or close it. Folded sections hide it, so unfold from the chevron first
All Off	Stop everything

Full detail in docs/CONTROLS.md.

The chord generator

The generator fills the current page of pads for a key and mode, so you can have a progression to play with before you know any theory. There is exactly one set of chord pads in Keys, and the Pads bar's own Fill and Regen write straight to them, so what you keep on a page is what you play. Its window also carries a 4x4 audition tray (2026-08-01) with a reference card above it: sixteen candidate chords that belong to no pad. Click one to preview it, drag it onto a pad to keep it - the cell it came from is left empty rather than refilling itself, which is what shows you which ones you have already taken. A candidate you never took is thrown away when the window closes; nothing in the window writes a pad any more except that drag (or the same commit through a tray card's right-click menu).

It is three chips, three combo boxes, a window (with its own tray, reference card and card menu), and two items on a pad's card menu.

Fill and Regen sit at the right-hand end of the Pads bar. Fill is the safe one: it writes chords to the empty pads and leaves everything already on the page alone. Regen is the one that overwrites, re-rolling the pads that already have a chord and skipping the ones you locked. Each greys out when it would do nothing, so you can see which is which.

Generator, beside them, opens the generator in a window of its own: every setting it has, a reference card, and a 4x4 audition tray of candidate chords, previewed with a click and dragged onto a pad to keep. The tray's own Fill, Regen and Clear buttons, on its header row, act on the tray alone - nothing in the window writes a pad any more. There is no page-wide clear left anywhere: Clear Page is gone (2026-08-01), and a pad still empties one at a time from its own right-click menu or by dragging it off the strip. Click the chip again while it is up and the window comes to the front rather than opening a second one; close it with its own Close button or the X in its title bar. It sits wherever you put it on the desk, remembers that place, and remembers whether it was open.

The reference card above the tray holds one chord none of the tray's actions can touch: drag a tray card onto it, or a pad from the main window (that drop copies the pad rather than clearing it). Left-click auditions it; Similar and Could follow fill the tray from it, and Clear empties it alone. Right-click a tray card for Send to first empty pad, fill the tray with similar chords or with what could follow, the three shaping edits, and New chord here / Clear this card - a new right-click menu, and opening it makes no sound.

Key, Mode and Scale Compliance are combo boxes on that same bar, left of the chips: the three settings you change while you are auditioning a page, one click to open and one to pick. They are the same three settings the window carries, so setting one from either place shows in the other. The bar is the fast way and the window is the complete one.

All six stay clickable when the pad strip is folded away, so folding the cards never takes the generator with it. Unfold and the page is written.

Two items stay on a pad's right-click menu, because they are about one card:

Item	What it does
New chord	A different chord for that pad's place in the scale (or, for a Markov chord, the next step of the chain)
Next: could follow	Chords that could follow this one, in four families: smooth voice-leading moves, circle-of-fifths, diatonic degrees, jazz substitutions. Every row has a play button to audition it before it drops into the next free pad

That same menu is where you Lock a card, and a lock is what stops a chord being replaced or thrown away: Regen skips it, Clear pad greys out, and dragging it off the strip no longer wipes it. A locked card shows a small dot in its top-right corner, and that dot is a marking rather than a button. Setting the lock is right-click only. A clickable padlock did sit in that corner for a few hours and came straight back off at Owen's request: on a small card it was a quarter of the surface, taken away from playing, dragging and feeding the arp, to save one click on a thing you set once.

The menu is also where Octave down / up and Next voicing move one card around without changing what chord it is. Voicing walks root position, then each inversion, then a spread that opens upward, and reads where it currently is off the notes rather than storing it, so it is the same chord sitting differently under your hand. All three work on a locked card, since a lock protects a chord from the generator and not from you; all three grey out while that card is the one being edited on the keyboard, because the keybed would write the unshifted notes straight back over the move.

The settings in the window: Key and Mode (12 modes), Octave (a range now, so a page can spread across registers), Scale Compliance (Algorithmic only: how far outside the key it may go - 100% stays in, lower borrows from related modes, then reaches for secondary dominants, then anything), Lock Influence (Algorithmic only: how much new chords copy the character of the ones you locked), Smooth Voicing (all seven sources, renamed from "Voice Leading" 2026-08-01: chooses which octave each note sits in so consecutive chords stay close, never which chords you get), Notes (a 2-11 range, replacing the old 3/4/5 tick boxes - below 3 you get dyads, above 5 the stack keeps climbing in thirds through the mode) and Inversions (root position plus 1st/2nd/3rd, which replaces the rotation a chord arrived in rather than compounding with it), two new sliders Brightness (a view onto Mode, sweeping the seven diatonic modes Lydian to Locrian) and Lean (nudges chords' thirds major or minor whatever the mode, 0 = neutral), six tick boxes that let any of Key / Mode / Octave / Notes / Inversions / Scale Compliance off the leash (unticked, the generator rolls that one freely), and Source, which since 2026-08-01 is seven always-visible buttons rather than a dropdown of two:

• Algorithmic, the weighted pool above, gated by Scale Compliance and Lock Influence.
• Markov: real-progression chains per Major / Minor / Modal, with Temperature (conservative to adventurous), Length, a Mood filter and a Start chord.
• Circle of Fifths: walks the circle from the tonic with a Direction (flat-ward or sharp-ward), landing on each degree's own diatonic quality where it's in the key.
• Neo-Riemannian: moves the tonic triad by P, L or R, weighted by three sliders - the smoothest, most key-ambiguous of the seven, since each move changes exactly one note.
• Progressions: transposes a named template (ii-V-I, the axis, 12-bar blues, Andalusian, Royal Road, rhythm changes, Coltrane's major-third cycle, or Random) to your key.
• Negative Harmony: mirrors the key about the tonic/dominant axis (C major becomes C minor). The one source with no settings of its own - Key, Mode and Octave are enough.
• Planing: slides one chord shape up or down, diatonically or (Diatonic off) chromatically, the constant-structure sound.

Each source's own controls take the place of the pool's row when you switch to it, since a row of settings that means nothing to a different brain is worse than no row at all - Algorithmic and Negative Harmony have no band at all any more, since Notes, Inversions, Scale Compliance and Lock Influence now live on fixed rows above every source rather than inside the pool's own. Mode greys out for Markov only - every other source still reads whatever it was last set to. Scale Compliance and Lock Influence are the ones actually dead outside Algorithmic. A read-only diagram under the Source buttons draws the shape whichever one is doing - the fifths wheel, the PLR triangle, the mirror clock, and so on - and highlights the walk that produced whatever's in the tray. Smooth Voicing (renamed from "Voice Leading" the same day) sits on its own fixed row rather than in any source's band: it's a pass over whatever the source produced, revoicing each chord to move as little as possible from the one before it, and it never changes which notes a chord contains, only which octave they land in. The choices are appended to the list, so a session saved as Markov still reopens as Markov.

Press any pad to hear it: its notes sit under the chord name on the card already, so there is nothing extra to turn on to read them while you work.

Driving it with Claude

Keys embeds an MCP server, so Claude Code (or any local MCP client) can set parameters, play notes and phrases, write and fire chord pads, and edit arp patterns directly — on either line, via an optional line argument that defaults to A. See docs/MCP.md.

Using it in Ableton Live

Keys loads as an instrument on a MIDI track and outputs MIDI, which Live routes into any other instrument:

1. Drop Keys on MIDI Track A.
2. On MIDI Track B, load your instrument (piano, synth, anything).
3. On Track B set MIDI From to Track A → Keys, and Monitor to In.
4. Click the on-screen keys. Track B plays.

Full walkthrough: docs/ABLETON_LIVE.md.

Installing

Grab KeysSetup-x.y.z.exe from Releases and run it — it installs the VST3 where DAWs look automatically (C:\Program Files\Common Files\VST3). Or build from source.

Building

Requires CMake 3.22+, Visual Studio 2022, a JUCE 8 checkout at ../JUCE, and the kit at ../okstudio-juce-kit.

The configure is quick again. Keys used to carry an audio-to-MIDI Transcribe section, which downloaded a multi-gigabyte prebuilt ONNX Runtime and forced the static MSVC runtime on the whole binary; both came with that engine rather than being choices. The section is gone, so neither cost is, and Keys is back on the default dynamic CRT. If you are reusing a build directory configured before that, pass -DOKSTUDIO_KIT_BASICPITCH=OFF once to clear the cached setting.

./build.ps1                 # VST3 -> %USERPROFILE%\Ableton\vst3
./build.ps1 -Standalone     # also build the standalone app

Or plain CMake:

cmake -B build -G "Visual Studio 17 2022" -A x64 -DKEYS_COPY_PLUGIN=OFF
cmake --build build --config Release --target Keys_VST3

Details and troubleshooting: docs/BUILD.md.

Accessibility statement

Keys exists because most on-screen keyboards and controllers quietly assume two hands and a keyboard. Its rules: every function is reachable with single left-clicks, drags, and scrolls, bar the right-click gestures Owen asked for (the chord-card menus - where Lock lives with no left-click twin, by his call - and releasing one note out of a pedal-held chord); no keyboard shortcut is ever required; no double-clicks, no modifier keys, no precision gestures on the critical path; large targets and high contrast. If something doesn't work for you with a mouse, that's a bug: open an issue.

License

Source is MIT (see LICENSE). Binaries link JUCE, which is licensed separately (AGPLv3 or a commercial JUCE license); distributing them must satisfy JUCE's terms.