digi-roll — piano roll for Elektron boxes

Edit ×

Notes

Velocity

Length

Probability

Pattern

Swing

P-locks

File

Drag a note's right edge to resize (hold shift for fine lengths); with a selection, they all move by the same amount · Length above makes them all equal instead · shift+drag for velocity · cmd/ctrl+drag sideways for micro-timing · alt+drag a note to duplicate it · right-click to delete. Paste lands where you last clicked. Trig conditions live in the PROB/COND/FILL lane under the grid, and p-lock automation in the lanes below that.

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Song

Genre

Bars

Root

Scale

Seed

Parts

Bass

Chords

Lead

Feel

Motion

Looseness

Humanize

Help ×

Getting a pattern onto your Digitakt 2 / Digitone 2

Everything happens in the Box panel (⇄). Both routes write straight into the box's pattern memory over USB — no live recording, no timing to get right — and both are safe: the destination pattern is re-read and downloaded as a backup first, only that one track's notes change, and the result is read back and checked byte for byte.

Draw something new → send it to a track

Connect the box via USB and pick it in the MIDI output menu.
Draw your pattern. Set the pattern length with the bars menu in the top bar.
Open Box, pick the destination pattern and track under Send to box, and press the button (it reads Send → A01 T1, naming exactly where it's going).
Check the confirmation — it names the pattern, the track and its sound, and how many trigs you're about to replace — then let the backup download. Done: the notes are in the box's sequencer.
If your pattern is longer than that track, the confirmation says so. The extra notes are stored, but the box only plays as far as the track's own LEN — raise it on the box (FUNC + PAGE) to hear the rest.

Optional: to hear the pattern while you draw, set Ch to the destination track's MIDI channel (SETTINGS → MIDI CONFIG → CHANNELS) and press Play. That's live monitoring only — it isn't how the pattern gets there.

Pull a track in → edit it → send it home

In Box, under Import from box, pick a pattern slot and press Fetch (this only reads).
Choose a track — the list shows each track's sound and trig count — and press Import into this slot. Its notes, lengths, velocities and micro-timing land in the slot you're editing (undo brings the old slot back).
Edit, then press Write back → A01 T3. The destination is already aimed at where the notes came from, and it refuses to write to a different box than the one they came from.
Want the edit somewhere else instead? Change the destination pattern/track and the button becomes a plain Send.

After a successful send the pattern remembers where it lives, so the next send is a write-back to the same place. Library keeps named saves in this browser — with swing, micro-timing and provenance — and exports them as .json.

Drawing

Click to draw a note and drag right to lengthen it · drag notes to move · drag a note's right edge to resize · shift+drag up/down to set velocity (brighter = harder) · cmd/ctrl+drag a note sideways for micro-timing (fractions of a step, shown as you drag) · alt+drag a note to duplicate it (the copy comes with you; drag the selection and the whole thing is copied) · right-click to delete, or alt-click and release without moving.

Selecting: cmd/ctrl+drag on empty grid draws a marquee · shift+click a note to add/remove it from the selection · moving, deleting, resizing, shift+drag velocity and the Velocity and Length sliders all apply to the whole selection.

Keys: space = play/stop · Delete/Backspace = remove selected · cmd/ctrl+Z undo, shift+cmd/ctrl+Z redo · cmd/ctrl+C / X / V copy, cut, paste (the clipboard follows you between pattern slots). Paste lands on the last cell you clicked, keeping the copied block's shape — click where you want it, then paste; anything that would fall off the end of the pattern or off the top or bottom of the grid is dropped rather than shoved into place, and you're told how many. Swing is per pattern (50 = straight) and travels to the box with a send — because it belongs to the whole pattern there, it re-times all 16 tracks in the destination slot, and the send confirmation says so whenever it would change what the box is holding. It comes back on import too. The scale menu only tints rows, it never restricts what you can draw. Patterns auto-save in your browser.

Note length, finer than a step

A plain edge-drag snaps to whole steps. Hold shift while dragging the edge for fine lengths, snapped to what the box can actually store and shown as a number next to the edge as you drag: sixteenths of a step up to two steps (0.125, 0.1875, … 1.9375), then eighths up to four, quarters up to eight, and so on — the hardware's own LEN scale, so what you see is what lands. Imported tracks keep their fractional lengths too; a 4.75-step trig comes in as 4.75 and goes home as 4.75.

Changing several lengths at once. Select notes (marquee or shift+click), then drag any one note's right edge: they all move by the same amount, so long and short notes stay long and short — a phrase keeps its rhythm instead of collapsing into one length. The group stops as soon as any member runs out of room before the end of the pattern, so nothing gets clipped and the relative shape is never broken. To make them all the same length instead, use the Length slider in the Edit panel: it runs along the box's own LEN scale, so every position it can reach is a length the hardware stores, and a note without room takes as much as it has. The slider also reads out whatever note you last touched, and follows an edge-drag as it happens.

One thing stays coarse on purpose: exported .mid files quantize length to 1/24 of a step. Chord notes used to share one length per trig — they hold their own now, along with their own velocity and micro-timing.

In the Edit panel: Dup bar adds a bar and copies the last one into it (up to 8), Clear empties the pattern, and Export .mid / Import .mid move patterns in and out as Standard MIDI Files — tempo, velocities, swing and micro-timing survive the trip, trig conditions don't, since MIDI has no concept of them.

Trig conditions (PROB / COND / FILL)

The strip under the grid is the box's TRIG page 1, one column per step. These belong to the trig, not to a note, so every note on a step shares them — exactly as the hardware works. A cell is only live where the step has notes.

PROB — drag up or down to set 0–100%, re-rolled every pass. This is a lock on that one trig, including at 100%; alt-click or right-click takes it off again.
COND — click for the picker: the eight logic conditions (PRE, NEI, 1ST, LST and their ! negations) plus every ratio from 1:2 to !8:8, tabbed by denominator. 2:4 plays on loop 2 of every 4; !2:4 plays on all the others.
FILL — click to cycle none → ON → OFF. ON plays only while FILL is held on the box; OFF plays only while it isn't. Unlocked ignores fill mode entirely — that's a real third state, not a synonym for OFF.

Probability — odds for the whole pattern

The Probability slider in the Edit panel sits under Velocity and Length, the way the box keeps the three together, but it works differently from those two: it is the track's own probability default rather than anything applied to the notes you've selected — the same byte the box holds: every trig runs at those odds unless it carries a PROB lock of its own, which wins. So "30% across the track, but these three trigs always" is a 30% slider plus three trigs locked at 100 — not a value stamped onto every step. Unlocked steps show the inherited number dimmed in the PROB row so you can see what they'll actually do. It's per pattern, it travels with write-back, cross-device copy and Library saves, and it's honoured in the browser preview.

Drag sideways to paint a value across steps · right-click (or alt-click) clears a cell · and if the step you click holds selected notes, the edit reaches every selected step at once. A conditioned trig is marked in the grid too: a dark corner flag on the note, plus the values written inside it once the note is two steps or wider. Conditions survive write-back, cross-device copy and Library saves; they are not in exported .mid files, which have no such concept.

Playing them here is a partial preview. Probability and the loop-counting conditions (1ST and every A:B ratio) are evaluated for real, so a 2:4 trig really does play every fourth loop. PRE, NEI, LST and FILL always play, because the browser has no neighbour track, no idea a pattern change is coming and no FILL button — the preview is never quieter than the box. Send it to the hardware to hear those properly.

Parameter locks (p-locks)

A p-lock is a parameter value stored on one step — a filter that opens across four steps, a decay that shortens on the last hit. On the box you hold a trig and turn a knob; digi-roll shows them as automation lanes stacked under the trig lane, one row per parameter, drawn as bars.

Add one in the Edit panel's P-locks group. The picker offers one box's parameters — the box this pattern came from, or the one you've picked in the MIDI output menu — because the two use different numbers for the same knob and a lane belongs to one of them. Then click in a lane to set a step's value from where you clicked, drag up and down to keep setting it, drag sideways to paint the same value across steps, and right-click or alt-click to clear. With notes selected, a click reaches every selected step. Values only land on steps that have a trig, because that's what a p-lock is.

Eleven parameters, the ones both boxes share: filter cutoff, resonance, filter env depth, pan, overdrive, delay/reverb/chorus send and LFO 1–3 depth.

You can hear them, and you can send them

Press Play and the box really does sweep. Lanes are sent as live parameter changes (NRPN, on the pattern's channel, just ahead of each step's trig), so you can draw a filter sweep and audition it against the notes without transferring anything. Those numbers come from Elektron's own published MIDI charts, so this part is solid.

And all eleven now transfer into the pattern itself. The internal numbers the pattern data uses aren't published anywhere — they were measured from real hardware, one knob at a time, on both boxes (they do differ: the same number means overdrive on a Digitakt II and filter frequency on a Digitone II, which is why lanes never translate by number). A lane whose parameter digi-roll hasn't measured still refuses to send, says preview only, and tells you why. The write path is hardware-tested on both boxes: lanes drawn here landed byte-identical and showed the right values on the boxes' own TRIG pages.

One thing to know before you press Play: auditioning moves the track's actual parameters on the box, and leaves them where the last step put them — exactly as if you'd turned the knob yourself. Reload the kit on the box to put them back.

Lanes already on the box

Import a track that has p-locks and you'll see every lane it carries. Lanes automating one of the eleven measured parameters come in named and editable, exactly as if you'd drawn them. A lane whose parameter isn't one of the eleven is listed and drawn in grey, read-only — digi-roll can see that lane 3 automates parameter 0x2B without knowing which knob that is — but it survives the round trip: edit the notes, send it back, and that automation lands exactly as the box had it. Library saves keep them, and a copy between two slots on the same box carries them. (One subtlety on measured lanes: the box stores locks slightly finer than one MIDI step, and digi-roll edits on the MIDI grid, so re-sending an imported lane rounds each lock to the nearest step.)

Two more things. Sending replaces that track's automation: lanes the box has and your pattern doesn't are cleared, the same way the trigs and their conditions are replaced — the confirmation names it before anything is written, and the usual backup downloads first. And a lock on a step with no trig (the box allows those) stays read-only rather than being edited, because digi-roll doesn't author them yet.

Chords

In the Harmony panel, turn on Chord draw and every click on an empty cell stamps a whole chord — a ghost shows what you'll get before you commit, and dragging right lengthens all of it. With a scale selected and quality on In scale, chords are diatonic: click D in C major and you get D minor, the V gets a dominant 7th, and so on. alt+wheel over the grid cycles the inversion, Spread opens the voicing up, and Strum staggers the notes with real micro-timing (it survives write-back to the box). Harmonize selection builds chords under notes you've already drawn. Chords are capped at 4 notes: that's exactly one trig's worth on the Digitakt II, whose trigs hold four note slots. The Digitone II can hold more, but digi-roll keeps the same cap so a pattern means the same thing on either box. Copying a fat chord onto a box that can't hold it keeps the four loudest notes and tells you what it dropped — never silently.

Generating a bassline, chords and a lead

The Generate panel (⚄) is somewhere between a randomiser and a session musician: pick a genre and a key and it writes three parts that agree with each other — a bassline, a chord part and a lead — into three pattern slots. Then send each slot to its own track on the box with the Box panel, exactly as you would a pattern you drew by hand. Nothing new is sent to the hardware: the generator only produces notes, per-trig conditions and p-lock lanes, and they leave through the same backed-up, byte-verified write path.

Genre sets the rhythmic grammar of all three parts — where trigs land, how long notes are, how hard they hit, and the groove. DnB (around 174) puts a long root anchor on the 1 and syncopates off the grid; Breaks (135) is funkier and full of soft ghost notes; Electro (130) is staccato sixteenths with octave leaps; House (124) puts the bass on every off-beat and stabs seventh chords between the beats. Each suggests its own tempo — there's a Set button, and nothing changes the transport unless you press it.

Root and Scale here are the same ones the Harmony panel edits, so the tinted rows on the grid always agree with what was generated. Progression is roman numerals in that key: i is the tonic, VI the sixth degree, i7 adds the scale's own 7th, i:2 lasts two bars. Type your own or press ↻ for another of that genre's. Each degree gets its natural quality from the scale — the same diatonic walk chord draw uses — so i VI III VII in C minor is Cm, A♭, E♭, B♭ with no chord tables anywhere.

The three parts, and why it's a band

They are generated in order — bass, then chords, then lead — and each one is handed what the previous parts are already playing. That's what buys call-and-response rather than three randomisers in a row.

Bass — roots, fifths, octaves and the chord's own seventh, with the occasional approach tone leading into the next chord. Downbeats hit hard, ghosts whisper. The 1 always plays.
Chords — one voicing per chord, with voice leading: of every inversion and octave that fits the register, it picks the one that moves least from the chord before it, so the part walks instead of jumping. Capped at four notes, which is one trig's worth on a Digitakt II.
Lead — a short motif is invented once and then developed across the progression: repeated, transposed, turned upside down, played backwards, shoved late. Notes on the beat land on chord tones; the ones between are free to pass through. And it answers the bass — a note that would land on a step the bass owns moves over or steps aside.

Density per part runs between that genre's own sparsest and busiest, so even 0 is music rather than silence — use the checkbox to leave a part out.

Feel: Motion, Looseness, Humanize

Motion draws p-lock lanes — filter contours that open across the loop, delay and reverb swelling into the turnaround, overdrive on the accents, pan movement on a lead. At 0 it draws none. A lane belongs to one box's parameter numbering, so it needs to know which box you're on: pick it in the MIDI output menu (or import a track from it) and it will say so on the status line if it still can't tell.
Looseness writes per-trig conditions, used for what they're actually for: 1:2/2:2 so a two-bar loop isn't two identical bars, 3:4 details that only arrive every fourth pass, PROB on ghost notes so the part breathes, the odd FILL trig. At 0 it writes none.
Humanize wobbles velocity and micro-timing so a repeated hit isn't machine-identical. At 0 you get exactly the genre's own numbers.

Two things it deliberately never touches. Swing, because that byte re-times all sixteen tracks in the destination pattern — genre groove (including house's shuffle) comes out as real per-note micro-timing instead, which is per note and yours alone. And the Probability slider, because chance belongs on per-trig PROB locks, which is how the hardware itself models it.

The seed

Every random decision comes from one number, so the same seed is the same music — shareable, and reproducible tomorrow. 🎲 rolls a new one and Generate arrangement rolls one each time unless you press 🔒. Lock it and each part still draws from its own stream, so nudging the lead's density leaves the bass exactly where it was: that's how you change one thing at a time. Re-roll the … does the slot you're editing on its own, keeping the seed — so you can keep a bass you like and try five leads against it, each one still answering that bassline.

Generating replaces the slots it's aimed at. It names them and asks first if there's anything in them, and the whole arrangement is a single undo step — one cmd/ctrl+Z puts all three slots back.

Fallback: capture by live recording

Only needed when digi-roll can't write to your box directly — an older Digitakt, a Digitone I, an Analog Rytm, or an OS build the pattern format hasn't been verified against yet (the app says so when you try to send). It plays the pattern out as MIDI while the box records it, so it's at the mercy of clock and timing; sending is better whenever it's available.

Connect the box via USB and pick it in the MIDI output menu.
On the box: SETTINGS → MIDI CONFIG → SYNC — enable CLOCK RECEIVE and TRANSPORT RECEIVE. Leave Send MIDI clock checked under Sync.
Set this app's Ch to the MIDI channel of the destination track (SETTINGS → MIDI CONFIG → CHANNELS on the box).
Select an empty pattern on the box, enter live recording (RECORD + PLAY), then press Play here. The app sends Stop → Start + clock, which snaps the box back to step 1 in sync with bar 1 of your pattern. Let it loop once, exit record mode, done.
Quantize on the box afterwards if needed. Notes longer than one step are captured with their length.

Sync rules (read this if notes land in the wrong place)

One clock master at a time. If your Octatrack (or anything else) is also sending clock/transport to the box, the box can't lock to this app. During capture either stop the OT's clock send, or set the Digi's SETTINGS → MIDI CONFIG → PORT CONFIG → INPUT FROM = USB so it only listens to this app — flip it back afterwards.
Every press of Play here sends Stop then Start, so the box restarts from its pattern step 1 — your recording always lines up with the app's bar 1.
Use Count-in (1–2 bars) to get a moment between arming live record and the notes arriving. Keep the count-in a multiple of the box's pattern length so the downbeats stay aligned.
On auto channel (default 10): notes go to whichever track is currently selected on the box — handy, just make sure the right track is active before recording.

Advanced: the device console

The device console is for the jobs the Box panel deliberately doesn't carry: whole-project backup and restore, importing from a saved .syx file, copying a track between patterns — or between the two boxes, and a raw SysEx log for when something needs proving. You never need it for the two routes above.

The desktop app

Digi-Roll Studio is the native version — a free, open-source desktop app for macOS, Windows and Linux that sequences several boxes in one session on a shared clock, rather than one track at a time in a browser. It also writes to an Analog Four, whose gen-1 pattern format this page doesn't know — six more tracks alongside the two digis' sixteen each. Same protocol work, same five write rules, no browser MIDI permissions. This page keeps working exactly as it does now.

Bugs, source and credit

Something wrong? Open an issue on GitHub. Please say which box and which OS build — the device console prints both when you connect — along with what you did and what happened instead. Writes are gated on a per-device OS-build allowlist, so "it won't let me send" is very often a box running a build the pattern format hasn't been checked against yet, and the build number is the first thing worth knowing.

If a write ever goes wrong, the pre-write backup .syx that downloaded just before it is what puts the pattern back — send it to the box from the device console. digi-roll never writes without taking one first.

Source, and patches, at github.com/zooloo303/digi-roll — plain HTML and JavaScript, no build step and no dependencies, so what you see in the browser is what's in the repo. By @zooloo303.

The SysEx protocol work is ported from elk-herd by mzero (BSD-2-Clause), whose source is the de-facto documentation of Elektron's protocol. The Digitone II pattern format wasn't documented anywhere, so it was mapped from scratch here by diffing real dumps; the byte-level write-up is in the repo's docs/ folder.