I've had Arturia's KeyStep for a few years now and I’ve always been impressed with the ease of use and the amount of functionality that Arturia managed to pack into it. Its big brother, the KeyStep Pro, has impressed me anew. The KeyStep Pro is a standalone controller for software, hardware synths, and modular devices, almost as if the Keystep and Beatstep had a baby. While the KeyStep Pro isn't huge, it isn't as small or portable as the KeyStep, and seems better suited to the studio rather than being carted out for fireside synth jam sessions. The Pro sports an easy to use and inspirational 4-track [polyphonic!] step sequencer, a drum sequencer, three arpeggiators, and a host of smart and user-friendly features that make it convenient, playable, powerful, and most importantly, fun to use.
The KeyStep Pro features a velocity-sensitive 37 key layout with aftertouch. They're mini keys and while not a particular joy to play, they feel about as good as one could hope for. They are pretty responsive and for my fingers, just on the right side of too small. The aftertouch and velocity curves can be adjusted a bit using Arturia's MIDI control center software, but even with the adjustments I didn't find that the keybed itself provided much travel or feedback. That being said, the keyboard feel is certainly not the main focus here. Pitch and modulation capacitive touch strips are on the left-hand along with a handful of control buttons for changing octaves, transposing sequences or arpeggios, adding in ties and rests and a key hold button. There are also four recessed looper touch pads at a few divisions for real time control over sequence looping.
Along the top half of the unit are the transport controls. Tempo, tap tempo and swing controls, a small OLED screen with encoder, and a few more utility controls [copy, paste, save, erase, etc.]. Next to that are the four [mostly] identical sequencer controls. Tracks 2-4 are the same, while track 1 has a drum sequencer instead of the arpeggiator. On the right are the step sequence buttons and five LED-ringed encoders for controlling various aspects of the produced sequences.
The KeyStep Pro is solidly built and heavier than it looks. The soft touch buttons are responsive and feel great. The small screen is crisp and easy to read. The LED rings are nice visual feedback in a sense but don't offer much in the way of precision. Luckily each of the five encoders is touch sensitive and the screen will change to show the value of the encoder as you touch it [before moving].
With the exception of a few settings the KeyStep Pro is menu free and the vast majority of the operations are available as either a direct button push or a shift + button [or shift + key press] combo. I personally don't mind a bit of menu diving in order to utilize certain functions but the KeyStep Pro's interface, once learned, is nice and immediate. At first there are a lot of button combos to discover and although they are well labeled, I did find myself squinting and hunting around for a particular function here and there even after getting fairly comfortable with the interface. Learning curve or not, the functions are clearly, and for the most part, intuitively labeled.
Along the back panel are all of the inputs and outputs. Power, a USB port, a sustain pedal input, a dedicated output and level control for the metronome, and 5-pin DIN MIDI ports [one in and two outs]. There’s also a clock in and out [along with a reset out], eight gate 3.5mm outs for the drum sequencer and four identical sets of outs for the four CV voices [pitch, gate, and velocity/modulation]. This connectivity is a real strong point for the KeyStep Pro and one that puts it on firm footing as a great one-stop-shop controller for a modular set-up.
Of the four sequencer tracks available, three can operate as arpeggiators. Each arp can be set to its own time division, quantized to its own scale, and run on its own pattern. Nothing particularly groundbreaking here, but I will say that having three independent arpeggiators so easily at hand and with the intuitive creative controls makes it easy to explore interleaving melodic patterns and interesting polyrhythms. Adding fuel to the improvisational fire are the encoders for gate, velocity, and randomness. The immediacy of simply tweaking the gate knob to move from staccato definition into a nice legato feel is great, and adjusting the velocity leads to a nice organic feel. The randomness encoder is a ton of fun as well and, coupled with the ability of the KeyStep Pro to play arps up to sixteen notes long, offers so much variety and exploration with so little effort that it starts to feel like musical cheating. The most recent firmware update also allows you to record arpeggios into a sequence so noodling around in arp mode until you find something you like and then grabbing it is easier than ever.
The step sequencers are also quite easy to use and intuitive. Each track can have a max of sixty-four steps [and it's super simple to set any number of independent sequence steps from 1 to 13 to 37... you get the idea]. Sequences can be entered on a step-by-step basis or recorded in real time. Keeping with the menu-less functionality are a variety of sequence controls available as “shift +” button presses. Sequences can be nudged forward and backward along the grid, transposed by semi-tones or octaves, and sent off the rails with a few random options. All four sequences are polyphonic, further widening the possibilities. This is the only place where I've stumbled a bit with the Pro, with the “shift +” commands. I've more than once mashed the wrong combination and sent my sequence spiraling off into randomized chaos, and at times even accidentally cleared a full pattern.
If an all-night arpeggio party isn't your thing and you'd like to add a little structure to your sequence noodling, the KeyStep Pro also provides its own form of arranging. Organized into projects that contain the four sequencer tracks, each track can contain up to sixteen patterns [sequences]. Moving between patterns is done with the navigation arrows on the respective track controls and the patterns can also be set up in chains [linked patterns that will play in a specified order] and further organized into scenes—a saved state of all the patterns and chains [or running arpeggios!] with each project able to store a total of sixteen scenes. Composing and arranging on the KeyStep Pro comes with its own set of quirks and the manual does a nice job of laying out a few strategies to organize everything within Arturia's paradigm.
As an all-around [and out-of-the-rack] controller for a modular system it is hard to beat the KeyStep Pro. As something that plays equally well with non-modular hardware synths as well as VSTs, its versatility alone is worth looking at. For me it is the immediacy of the arpeggiators, sequencer tracks, and keyboard that make for a very frictionless creative experience. The additional parameter controls available, Arturia's well thought out interface layering, the multiple tracks, simple to execute pattern chaining, and arrangements, and above all, the ease of which the various components work together make the KeyStep Pro a strong contender for a desert island controller.

Price: $449

arturia.com