Also - sorry for the double comment. The design was definitely influenced by similar form factor keyboards like the Op-1 and QuNexus although the latter does not use actual keys but is an MPC like pressure sensitive pad rather than a push/levered/actuated key. Also, in general, the design was influenced by the status quo of how producers / musicians approach such MIDI instruments and why/how they're used.

The biggest difference in our design is the exclusion of all controls, buttons knobs and so on which means that even though the Keys device is about the same size as some of these other portable devices, the keys themselves are nearly the same size and layout ratios as traditional. In other words, full size keys not mini size which is hard to tell in the pictures. This feature, of both our personal opinions and the feedback of professionals we gave Keys to, is significantly more important than any other in a truly useful as well as portable keyboard.

The fact that all controls are removed and the design is purely keys also allows for the modular nature, and the ability to connect Keys together in various ways as well as other modules.

The proximity sensor is indeed an IR based sensor similar in design to the D-Beam that Roland employs in some of their keyboards. The impetus for these sensors was the need to add a swipe gesture to transpose the keyboard up and down - the actual distance detection was a nice bonus which we exposed by it outputting control channel data.

Each sensor sends on a separate control channel, and when linking multiple keys devices together, the control channels are transposed so adjacent keys sensors each send CC on their own channel (so each sensor is mappable, and in the same fashion for a given configuration of devices)

This is one of those learned things that becomes inborn, I think.

I have a few things I'm pretty good at, and I'll pick up & try anything, because it's fun. Most of the music I make is improvised. And I've been picking up & trying any instrument I run across for decades now, so I have snippets of experience in lots of things now.

My wife studied classical piano from an early age, and can sit down and sight-read stuff I haven't got a chance at playing on any instrument. But she never improvises, never tries out other instruments, and thus can't really do the same thing (pick up anything and make music on it).

We both have a (possibly-inborn) talent for music, but we've taken quite different paths, and those years spent quite differently really show, now.

Ideally the dream keyboard would have BOTH.

For playing piano, and other player-volume controlled instruments, you want velocity sensitivity.

For organ, or maybe early electric "pianos" you don't...you want an expression/volume pedal. This is one reason a virtuoso organ player can do things a piano player couldn't - they can use all kinds of "wrong" reachs and finger movements that enable them to play things that they couldn't otherwise.

Keys has per-key key velocity implemented.

Keys has very close to full ratio keys to a standard piano. If you take it and put it up against a normal piano you'll see the keys span about the same length as two octaves, maybe by a difference of 2-3 mm.

This was a very critical aspect of the design and actually led to the implementation of the proximity sensors. We had to remove all controls to get this size but still be about the width of a 13" laptop - and the need for certain controls like octave transposition was the impetus for looking into other control methodologies like proximity based gestures.

Interesting -- I'd be curious to see what actual musicians would say. It really depends on the type of music you're building with it, I'd say.

I'm not primarily a keyboardist, but I use them; in this case it would surely be tricky to play anything that uses the black keys much; your hands have patterns memorized that (I'd imagine) would be tough to adapt to having the black keys on a separate row.

But because it's MIDI, it really does depend on what you're building, and it might not matter. Recording simple snatches of melody would be fine if you keep away from chromatic lines -- e.g., if you want to add a line that's in C minor, just record it in A minor (all white keys except maybe the G#), then transpose it in a few seconds.

You wouldn't play the Flight of the Bumblebee on it, though.