Arturia unveils KeyStep 37 mk2

The original KeyStep 37 earned its place on desks and stages worldwide for good reason. Compact, versatile and genuinely playable, it sat at a sweet spot between minimal keyboard controllers and full-blown production rigs. With the mk2, Arturia has not simply refreshed the aesthetics. The revisions run deeper than that, addressing real-world limitations whilst adding tools that push the instrument into decidedly more creative territory.

The headline additions are Mutate and the Phrase Arpeggiator, both designed to keep sequences evolving without stopping the music. Alongside these sits an updated OLED screen, a second CV Mod output, USB-C, a dedicated power switch and a strip of 39 LEDs above the keybed that tracks notes in real time. On paper it reads like a targeted upgrade. In practice, it changes how you interact with the instrument.

What’s Actually Different

Physically, the mk2 adds five keys, two extra buttons and four dedicated encoders for navigating sub-menus. That might sound incremental but the effect on workflow is significant. Where the original required multiple button combinations to access deeper settings, you can now reach them directly. Less menu-diving means more playing.

The OLED display is a genuine upgrade over what came before. Feedback is immediate and readable, which matters when you are mid-set and need to confirm a parameter without guesswork. The LED light guide above the keybed is similarly practical, visualising note output in a way that is useful for both performance and understanding what the sequencer is actually doing.

On the back panel, the second Mod output is a welcome addition for anyone running a modular or semi-modular setup. You can now assign Mod 1 and Mod 2 independently to aftertouch, velocity, mod wheel, a random per-step signal or a pulse per step. Paired with CV Pitch and Gate, this gives you four simultaneous CV outputs from a device that fits in a backpack.

Sequencer and Generative Tools

The sequencer remains the core of the instrument and it has been strengthened. Pattern chaining allows you to link sequences into longer structures, which opens up genuine song-building from a device that previously felt better suited to loops. Unquantised recording is now selectable via a long press on the Seq button, letting you capture natural timing rather than forcing everything to the grid.

Mutate is where things get interesting. Press the button and the current sequence or arpeggio is transformed, anywhere from subtle variation to something considerably more unexpected. It operates on the fly without stopping playback, which means you can use it as a live performance tool rather than a studio-only feature. The degree of transformation is not random chaos; it retains melodic and rhythmic coherence whilst introducing genuine variation.

Spice works alongside Mutate, accessed via Shift and the mod wheel. It injects controlled randomness into rhythmic patterns, keeping sequences moving in ways that feel human rather than mechanical. Used together, Mutate and Spice give you the sense of a sequence that is always developing, which is exactly what you want in a live context.

The Phrase Arpeggiator adds a different dimension again. Rather than cycling through notes in a fixed up-down pattern, it loops a generated phrase built from whichever notes you are holding. Each of the pattern arpeggio styles, accessed via keys 7 through 15, produces different phrase densities and feels, from sparse and sparse to busy and polyphonic. Hit Mutate on top of a Pattern Arp and the phrase shifts into a new variation without dropping the beat.

Connectivity

The back panel is well specified for this form factor. USB-C handles both power and MIDI over USB, replacing the micro-USB of the original. MIDI In and Out cover hardware routing. Sync I/O keeps the unit locked to external clock sources such as drum machines and modular gear. A pedal input adds expression or sustain depending on assignment. The Kensington lock slot is a small but sensible addition for live use.

The power switch is new and more practical than it sounds. Being able to power down without unplugging USB is particularly useful in studio environments where the unit is part of a larger signal chain. These are the kinds of refinements that come from listening to how people actually use gear rather than from a product roadmap drawn up in isolation.

Playability

The 37 slim keys with velocity and aftertouch sensitivity remain one of the better keyboard actions in this price bracket. They are not weighted, and nobody should expect them to be at this size, but they are responsive and consistent. Aftertouch in particular is well calibrated, providing enough resistance to prevent accidental triggering whilst remaining accessible during sustained passages.

Chord mode is worth exploring in depth. Holding the Chord button whilst pressing keys sets a chord shape that follows whatever note you play subsequently. The Velocity Spread setting controls how many notes within that chord sound based on how hard you play, which introduces an expressive dimension that can make even simple chord progressions feel dynamic. Pair it with a Scale mode to stay in key and the results are immediate.

Gate Length Control allows you to shape note duration across the sequence, moving from staccato to legato with a single parameter. It is the sort of feature that sound designers will reach for constantly, and it works equally well whether you are sequencing a synthesiser or sending CV to a modular voice.

Verdict

The KeyStep 37 mk2 is a measured and confident evolution of a product that already worked well. Arturia has not over-engineered it. The additions serve the instrument rather than pad a spec sheet, and the overall experience is of a device that has been refined through genuine use rather than committee.

Mutate and the Phrase Arpeggiator are the standout features for anyone interested in generative approaches to composition. The expanded CV connectivity makes it compelling for modular users. And the improved physical controls and OLED display raise the practical ceiling for live performance. At this size and price point, it is difficult to find a comparable instrument that does as much as this one.

For producers working at the intersection of hardware and software, for performers building hybrid live sets, and for anyone who wants a compact controller that does not compromise on depth, the KeyStep 37 mk2 makes a strong case for itself.

AT A GLANCE

Keys: 37 slim keys, velocity and aftertouch

Sequencer: Polyphonic, pattern chaining, unquantised recording

Arpeggiator: Classic and Phrase modes, Spice, Mutate

CV outputs: Pitch, Gate, Mod 1, Mod 2 (new)

Connectivity: USB-C, MIDI In/Out, Sync I/O, Pedal input

Display: OLED screen, 39-LED keybed strip

Find out more here

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