keystep-mods

Mods for the Arturia KeyStep Pro: new features for its firmware, applied to your own copy of the official update. Pick the mods you want, build a patched update in your browser, and flash it with MIDI Control Center like any other update. Flashing the stock update puts the original firmware back.

Open the patcher to see the mods in action and build your update.

[!WARNING] At your own risk. These mods are unofficial changes to the KeyStep Pro firmware, not made, checked or supported by Arturia. You flash them entirely at your own risk and responsibility. They come as they are, without warranty of any kind, and the author is not liable for any damage, data loss or malfunction of your instrument. Flashing the official update puts the original firmware back.

The mods

generative: Generative tracks. Flux on Tracks 2 to 4, a melody loop that keeps changing; Pulse on Track 1, drum pulses spread evenly over each drum lane's steps (below).

Flux: a loop of 8 steps that keeps changing Pulse: drum lanes spreading their hits around rings

filter-midicc: Clean pattern switches. A pattern switch no longer re-sends Bank MSB, Bank LSB and Program Change when that MIDI channel already has them, so the first note after a switch is no longer late on synths that reload their sound on every program change. Play and the first key send each track's sound, so the synth is right from the first note after power-on (below).

Play, then pattern switches: stock sends no sound on Play and re-sends it on every switch; with the mod Play sends it once and the switches are on time

track-cc: Control mode follows selected track. In Control mode a knob on the Global channel sends its CC on the MIDI channel of the track you came from, so it reaches the synth that track plays (below).

Control mode follows selected track: stock sends the knob CCs on channel 1 whatever track Control mode came from; with the mod they go to that track's channel

Mods combine: tick several and they go into one update. generative and filter-midicc have been flashed to a real KeyStep Pro, and Generative tracks has been played on it; track-cc has not been on a real unit yet.

They only work on KeyStep Pro firmware 2.5.20, on both the standard KeyStep Pro and the KeyStep Pro Chroma. The page checks that your file is the untouched 2.5.20 update before it changes anything. If MIDI Control Center offers a newer firmware, the mods do not apply to it.

Flashing a patched update is at your own risk. The page and the MIT licence come with no warranty.

Building a patched update

Get the page. On GitHub, download this repository as a ZIP (the green Code button, then Download ZIP) and unzip it. Double-click web/index.html to open it in your browser. It works offline, straight from disk.

Find your stock update file. MIDI Control Center installs it. On Windows it is C:\ProgramData\Arturia\MIDI Control Center\Firmware\keystep-pro_Firmware_Update_2.5.20.0.kspf. On macOS it is in MIDI Control Center's firmware folder. Keep a copy of this file somewhere safe: it is how you go back to stock.

Build. Drop the stock file onto the page, tick the mods, build, and save the result. Everything happens in the browser; the firmware is not uploaded anywhere.

Flashing it

Connect the KeyStep Pro to your computer by USB.
Open MIDI Control Center and select the KeyStep Pro.
Go to its firmware revision and click Upgrade.
Choose the patched .kspf file you saved.

MIDI Control Center keeps working normally with the patched firmware: projects sync as usual. It may offer to update the firmware; doing that puts the stock firmware back.

Going back to stock

Use the same steps, and choose the stock update file instead (the one you kept a copy of). That puts the original firmware back.

If it does not start

The KeyStep has its own recovery mode, and it always lets you flash again:

Power the KeyStep Pro off.
Connect a cable from Clock In to Reset Out.
Power it on.
Remove the cable.
In MIDI Control Center, flash the stock update (or a patched one) as in Flashing it.

Generative tracks (the `generative` mod)

The generative mod adds something the KeyStep Pro does not have: tracks that write their own music.

Flux (Tracks 2, 3 and 4): a short loop of random notes that repeats, and changes a little on every pass.
Pulse (Track 1): every drum lane spreads a number of pulses as evenly as possible over a number of steps.

If you know modular synths: Flux is a Turing machine, Pulse is Euclidean rhythms.

Entering and leaving

Track 1 can only be Pulse (with its Seq and Drum buttons). Tracks 2 to 4 can only be Flux (with their Seq and Arp buttons).

Every track has a Seq button and an Arp button (Track 1: Seq and Drum). Normally you press one of them to pick the track's mode. Hold Seq and press Arp (Track 1: hold Seq, press Drum) and the track goes generative. Both buttons light up, which no stock mode does, and that is how you know.

Press Seq or Arp/Drum on its own and the track is back in that normal mode, with its pattern exactly as it was: generative mode only plays instead of it, and never writes into it.

Each track goes generative on its own, so you can run Pulse drums on Track 1 under a Flux line on Track 2 and a sequenced bass on Track 3. A generative track plays through the KeyStep's own sequencer, so it behaves like any track: its own MIDI channel, CV/gate outputs (Track 1: the drum gates), Play and Stop, tempo, swing and Mute. Press Play, or Shift + Play while it runs, and every loop starts again from its first step.

While the selected track is generative, the five encoders above the step buttons set the generator instead of the usual step parameters. Touch a knob and the OLED shows what it does and its value (drawn in the Flux and Pulse tables below), the way the stock firmware shows its own encoder popups; otherwise the screen shows what it normally does.

Flux (Tracks 2 to 4)

Flux: an 8-step loop playing, with a step now and then changing to a new note

Flux is a short loop of random notes that repeats, and changes a little on every pass, as much or as little as you allow. Locked, it is a riff that never changes. Wide open, it never plays the same thing twice. In between, it wanders: a phrase that slowly changes while you play over it.

The five encoders:

encoder	range	what it does
Pitch	1 to 36 semitones	Range: how far the notes spread around middle C, half the Range below it and half above. The notes are then snapped to the track's scale and root. 12 is one octave
Gate	1 to 16 steps	Loop Length: how many steps the loop has before it repeats
Velocity	0 to 100 %	Density: how many of the steps play a note; the rest are rests
Time Shift	0 to 100 %	Change: the chance, per step and per pass, that the step gets a new random note. 0 locks the loop
Randomness	any turn	Riff: throws the loop away and makes a new one

The first time after power-on, a Flux track starts at 8 steps, Range 12, Density 75 % and Change 10 %: a one-bar phrase that drifts slowly.

Scale and Root (Shift + keyboard, as on a normal track): Flux's notes are snapped to the track's scale and root, so Minor or Blues with a root of D keeps every note in D minor or D blues.

Last Step + Step N sets the loop to N steps. The 16/32/48/64 page buttons do nothing there: a generative loop is 16 steps at most, and your stored pattern's length is left as it is.

Last Step + Step 6: Loop Length, 6 steps

Press a step to turn it off (a rest) or on again (it plays its note). The step buttons only ever change the loop in Flux: holding a step and playing keys does not write into your stored pattern.

On the step LEDs, magenta flashes on a step at the moment Change gives it a new note, so you can see the loop change.

Pulse (Track 1)

Pulse: three drum lanes as rings of dots, each with its own pulses and length, played round together

In Pulse, every drum lane spreads a number of pulses as evenly as possible over a number of steps. A drum lane is one drum sound, one per key of the lower two octaves, as in Drum mode. 4 pulses over 16 steps is four on the floor, 3 over 8 is the tresillo. Give each drum its own count and length and the lanes drift against each other into grooves that take a long time to repeat.

There are 24 drum lanes, one per key of the lower two octaves. Press a key to pick its drum lane, as in Drum mode; the five encoders then set that lane:

encoder	range	what it does
Pitch	0 to 100 %	Dynamics: how much the velocity of this lane's hits varies. At 0 % every hit plays at velocity 100; turn it up and each hit gets a random velocity, from about 30 to 127 at 100 %
Gate	1 to 16	Steps: the length of this lane's loop
Velocity	0 to Steps	Pulses: how many pulses, spread as evenly as possible over the steps. 0 silences the lane
Time Shift	0 to Steps minus 1	Rotate: moves the pulses later, so the same rhythm starts on another step
Randomness	0 to 100 %	Chance: the chance that each pulse plays: below 100 % the beat starts to breathe

The first time after power-on, Pulse starts with a plain beat to build on: kick (the first key, note 36) 4 pulses, snare (note 38) 2 on the backbeat, closed hat (note 42) 8, all over 16 steps.

Last Step + Step N sets the picked drum lane's Steps to N. The 16/32/48/64 page buttons do nothing there: a generative loop is 16 steps at most, and your stored pattern's length is left as it is. A step press on its own does nothing in Pulse: the hits come from Pulses and Rotate.

The KeyStep's own settings still work

A generative track listens to the same Shift + keyboard settings as a normal track, including the blue LEDs that show them while Shift is held:

Scale and Root (Flux): see Flux;
Time Division and Triplet: 1/8 plays half as fast as 1/16, triplets play in threes;
Fwd / Rand / Walk: the loop follows the track's playback direction, as a stored pattern would: it runs forward, jumps to random steps, or walks (next step, previous step or the same one).

What the step LEDs show

The step buttons show the loop itself, not the stored pattern (on Track 1: the picked drum lane):

A Flux loop of 9 steps: notes teal, rests dim, the playhead white, a step that just changed magenta, steps 10 to 16 unlit

lit steps are the loop: 9 lit steps is a loop of 9;
teal is a step that plays (a note, or a pulse), dim is a rest;
white is the playhead;
magenta (Flux only): a step that just got a new note, see Flux.

The track display

The track's display shows what the track is doing instead of a pattern number: FL for Flux, PU for Pulse. The track display can show FL and PU because the mod also updates the chip that drives the panel.

Settings kept until power-off

Flux and Pulse settings are kept per track until power-off: leave generative mode and come back, and they are as you left them. Nothing is saved to the project.

Keep what you hear: Record

Record works as it always does: press Record (while playing, or before Play) and every step the track plays is written into the pattern it is on as the playhead passes; press Record again to stop. Let Flux or Pulse run, and record once it plays something you like. The track keeps generating while it records, so what ends up in the pattern is exactly what you heard, changes included. Leave generative mode (Seq, or Drum on Track 1) and the recording plays on from the same step.

Flux writes each note with its velocity, a rest as an empty step, and sets the pattern's Last Step to the loop length.
Pulse writes each drum hit as it plays, at the velocity it played at, with the lane's own length, so lanes of different lengths keep drifting against each other in the pattern too.
A recorded step replaces what that step held. Save the project as usual to keep it.

Not stored, on purpose

Nothing about generative mode itself is saved. Power the KeyStep off and every track is back to its normal mode, with its patterns as they were. That is deliberate: a project on the KeyStep is exactly what MIDI Control Center syncs and copies, and generative mode keeps out of it. If a loop is worth keeping, record it (above).

Clean pattern switches (the `filter-midicc` mod)

Play and four pattern switches compared: stock plays the synth's own sound after power-on and then reloads the sound on every switch, each note late; with the mod Play loads the sound once and every switch plays on time

A pattern can send a Program Change with its Bank MSB and LSB when it starts (Shift + Track > PC Assign). The stock firmware sends all three on every pattern switch, even when the new pattern's values are the same as the old one's. A synth that reloads its sound on every program change (a Roland JV-1010, for one) then plays the first note after a switch late.

With filter-midicc the KeyStep remembers, per MIDI channel, what it last sent since power-on, and a pattern switch sends nothing when that channel already has those values. Any difference sends all three as before. The first switch after power-on always sends.

Play also sends each track's sound, which the stock firmware never does, so you can switch the KeyStep and the synth off and on as often as you like:

Play always sends every track's sound, so the synth has it from the first note after power-on, and a synth switched off and on on its own gets it back at the next Play.
The first key after power-on, or after Stop, sends the current track's sound before its note. The next keys send nothing.

If you change the sound on the synth by hand, a switch to a pattern with the same Program Change will not send it again. Switch to a pattern with another program, or flash the stock update, to get the old behaviour.

The mod only affects Bank Select and Program Change sent on a pattern switch. Nothing else changes.

Control mode follows selected track (the `track-cc` mod)

Control mode entered from Track 2, 4 and 1 in turn: stock sends the knob CC on channel 1 every time, with the mod it goes to channel 3, 12 and 5

Press Control and the five knobs above the step buttons send MIDI CCs (CC 74 to 78 unless you changed them in Utility > Controller > Knob 1..5). Stock, every knob left on its default channel, Global, sends on the Global MIDI channel (Utility > Controller > Global MIDI chan, channel 1 out of the box), whichever track you were on.

With track-cc a knob on Global sends on the MIDI Channel OUT of the track you entered Control mode from instead: the track whose button blinks while Control is on. Select Track 2, press Control, and the knobs reach the synth Track 2 plays, say a JV-1010 on channel 3, to sweep its cutoff and resonance. Select another track, press Control again, and the knobs follow that track's channel. Track 1 in Drum mode uses its Drum Output channel.

No new settings. The mod adds no menu choice and stores nothing: settings and MIDI Control Center work and save exactly as on stock. Global simply means "the track's channel" in Control mode.
CC numbers, Port, Min and Max stay as set per knob.
A knob set to its own channel (1 to 16) keeps sending there. Use that for a knob that should always reach one synth.
Outside Control mode nothing changes.

For developers

You do not need anything below to use the mods: the browser page does everything.

Building from the command line

Python 3, pip install keystone-engine, and for C mods the Arm GNU Toolchain:

python patches/make_patch.py generative filter-midicc   # -> keystep-pro_Firmware_2.5.20+generative+filter-midicc_mods-<release>.kspf

make_patch.py and the web page both refuse any file that is not the exact stock 2.5.20 update, and both give byte-identical output. The update file holds firmware for both the main chip and the panel chip, for both models (the standard KeyStep Pro and the Chroma). Every mod is built for both models, and MIDI Control Center flashes the set that matches your device.

How a mod is made

A mod is only our own bytes: its source (C or assembly), the firmware addresses it hooks, and the flash and RAM it uses (patches/<mod>/patch.json, patches/free_space.json). Arturia's firmware is never stored or distributed here; make_patch.py and the web patcher read it from your own update file and check its SHA-256 before changing anything. Each mod has a fixed place in flash and RAM, so mods combine, and two mods that overlap or hook the same instruction are refused. After changing a mod, python patches/make_patch.py --export regenerates the web patcher's copy (web/patches/).

web/ - the patcher page (index.html, kspatch.js) and the exported mods (patches/).
patches/ - make_patch.py, the free flash and RAM, and one folder per mod.
docs/ - how each mod hooks the firmware: docs/GENERATIVE.md, docs/FILTER_MIDICC.md, docs/TRACK_CC.md.

Changes

Current version: 1.1.1. What changed in each version is in CHANGELOG.md.

Licence

MIT, see LICENSE. Arturia and KeyStep Pro are trademarks of Arturia; this project is not affiliated with Arturia.

Looking for more cool stuff? I also release open source audio VST plugins as WET VST.