Sophia
Haha! My apologies! But there is a fun story on why I found that piano on Google. I was eating black licorice (which I love) and some of it got stuck between my teeth and when I looked in the mirror I thought my teeth looked like a piano keyboard, which was hilarious. So I went on Google to search for "piano teeth", and found our feline friend!
This talk of small keyboards made me wonder about something. I’ve heard about pianos being fitted with a 7/8 keyboard, which is something I would like to do with my piano but never will. If I could find a digital piano with a weighted 7/8 keyboard, I would be all over that. Does anyone even make those?
Yamaha C5X
Cassia If I could find a digital piano with a weighted 7/8 keyboard, I would be all over that. Does anyone even make those?
They are out there, but typically created by very niche manufacturers. Here's an example:
There are also pianists who have had their digitals (MP11, etc.) modified with narrow keys. I'm sure at great cost!
Cassia As far as I know, the NK5.5 featured in the video above is currently the only controller with (somewhat) weighted keys on the market, though still not mass produced to the numbers required for an off-the-shelf product and still only available to US customers, I believe. The Dutch company Kaduk had their "Respons" controller in the pre-production for years. It should supposedly be available in custom ordered sizes down to 3/4 of standard width and with a much more traditional piano like action than the "touch-weighted" NK5.5. When I looked at the Kaduk website just now it appears they are relocating at least part of the company to Poland. Maybe they are finally getting ready for actual production? The new Respons webpage doesn't mention custom sizes any more and they've cut most of the handfast info on the product https://www.kaduk.nl/flagship-projects/respons. Their "ergonomic interfaces" seem to have been branched off to a new brand called Fairkey but maybe that is intended for acoustic piano actions only. If my memory serves the intended price point for the Respons was roughly 3000€ a few years back. I think it was mentioned by T. Kaduk, owner of the company, in an old PW discussion.
You could also check the Pask-piano web site, but there are currently no other digital piano manufacturers mentioned there. https://paskpiano.org/manufacturers/
Personally I think a choice of key sizes would be the most meaningful update to the digital piano market, but as for myself I'm not holding my breath any more but decided a few months back to try to build my own controller from scratch. I'm expecting it to be a very time consuming endeavor given all things I still have to learn and design.
This youtube vid is a good watch that talks generally about narrower-key pianos. But it's particularly germane because the pianist narrator has an MP11SE, for which he had David Steinbuhler create a DS-6.0 keyboard:
He said it was $5000 for the new keyset (on top of the $2-3000 of the MP11SE itself).
I think the main issue with the small keys is how much you're going to limit yourself in terms of flexibility in terms of hardware.
I can choose from this one or that one and none of the hundreds of others even though they are nicer/cheaper/whatever.
Google tells me that the current standard key width has been in use since about 1880 so there's a lot of inertia there.
Just like with the folks who occasionally show up on this forum with alternative keyboard layouts, it's going to be difficult to get any traction in the face of the magnitude of standard equipment.
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If you're a zombie and you know it, bite your friend!
FrankCox I think the main issue with the small keys is how much you're going to limit yourself in terms of flexibility in terms of hardware.
Part of me agrees, but I do think that much of the concern is likely unfounded.
1) Lots of instruments come in different sizes, so I don't believe that piano is inherently more 'one size fits all'. I get that some instruments are more personal (in that the player carries their own around), where as piano performances are "you play what is there." But...
2) Most people who experience these narrower keyboards report very little trouble adapting/adjusting. For some it's a few minutes or a few hours, but most find they can move back and forth between narrow and full-sized fairly easily.
3) I suspect a lot of full-size-only-players may retreat to an intuitive (but likely incorrect) mindset of "your brain will get confused by having to adjust," similar to how people who only know one language are often heard saying "how do you process so many more words for multiple languages? Doesn't your brain get too full/confused/mixed-up?" In reality, it just doesn't work that way, talk to anyone who is fluently multilingual, and switching between languages is more or less natural. People can adapt to driving different cars, hop on a skateboard immediately after biking, switch between writing cursive and printing, etc. This is just getting used to a different variation.
However, I totally agree that the inertia is against any kind of widespread adoption, and there have been a lot of folks on PW who were actively opposed to the idea that anyone should pursue a narrower keyobard--IMHO, that's unfortunate. I do hope that with more visibility, the existence of narrower-keyboard options gets a bit wider exposure, and regardless of what the rest of us think about its practicality/learnability/etc., those who might find it useful have some resources to pursue it on their own!
Something I would find interesting is how an average pianist would adjust to various sized keyboards on the fly, as in sit down to one size, play one song, sit down to another of a different dimension keyboard, and play another song, etc, no rehearsal, no previous time spent, just sitting down cold and playing.
I can't speak for others but I might think that a small change might be a non-issue where a significant size difference might not work at all, at least without a little time to adjust. Having never experienced it personally, it's hard to speculate.
Bellyman in college, I took a semester of harpsichord lessons. I never went immediately from piano to harpsichord (or vice versa) but often played both in the same day. I’m kind of fuzzy on details now but I remember there was an adjustment period. It wasn’t extreme but it would take some small amount of time to adjust from one size keyboard to another. Probably with more exposure, it would have gotten easier and faster.
Yamaha C5X
Cassia in college, I took a semester of harpsichord lessons. I never went immediately from piano to harpsichord (or vice versa) but often played both in the same day. I’m kind of fuzzy on details now but I remember there was an adjustment period. It wasn’t extreme but it would take some small amount of time to adjust from one size keyboard to another. Probably with more exposure, it would have gotten easier and faster.
I've often switched between piano and harpsichord. The keys of most harpsichords are nearly the same width as piano keys. The more important difference is the length: harpsichord keys are usually shorter than piano keys. This takes a bit of getting used to, and makes you understand why baroque keyboard players didn't use their thumbs as much as we pianists do.
The key dip is less than that of a piano, and of course the touch is completely different: there is no dynamic response, either the note sounds or it doesn't.
Despite these differences, I'm able to switch pretty fast between the two instruments, even immediately if necessary.
MRC I've often switched between piano and harpsichord.
I have never played a harpsichord. 
Once upon a time, I was a piano tech and rebuilder. I had collected a couple of grand pianos to rebuild and picked up a harpsichord that someone had started but never finished, nowhere near playable. And then... Hurricane Katrina came through and wiped that all out. That's about as close as I've ever come. Life didn't see me continuing in that line of work after that and I don't even have an acoustic piano anymore.
Bellyman Yes, it looks effortless for her. Possibly she looks more than otherwise expected at her hands?
I also play a bit of classical guitar and own a "lady" size guitar with a scale length of 62 cm as well as a couple with the standard 65 cm scale. I find it very easy to go between the sizes, but I believe I may glance a bit more towards the guitar neck when aiming for a long shift with the left hand if I've just switched instrument sizes. I can't imagine it would be more difficult to switch between piano keyboards. Obviously assuming the instruments are similar otherwise. Switching between instruments with very different responses is of course another matter.
I expect there is some variation and super-optimized muscle memory, particularly at the highest levels of play!
But I might think that for smaller-handed pianists, the burden/difficulty/injuries from straining to hit 8ths, 9ths and 10ths regularly might for some far outweigh the inconvenience of learning to adjust to a slightly different action.
That's so interesting! I'm paging @Nightowl too because she and I were actually talking about what a keyboard with more narrow keys would do. Apparently, the brain adjusts without effort. I think that means we're both one step closer to buying a cutesy little keyboard with the excuse that it will make us practice more 
Gombessa There's also a lot of repertoire that is literally out of reach when all available pianos are too big and one is only able to reach e.g. an octave on them.
I grew up with a piano in the house, but when I was old enough to pick an instrument to learn formally, piano was never really on my radar. I could read the method books and sheet music left on the piano music stand by my older sibling and mother well enough. I knew what keys were which on the piano, thus realizing that I couldn't reach some of what was even in the beginners' book, so why choose an instrument that was obviously such a bad fit, I thought. As an adult I can strainfully reach an octave on the edge as well as on the black keys, but even in my early teens that felt like something I might never be able to do.
When I much later decided to learn piano during the pandemic I was baffled that digital pianos only came in one size, especially considering that so many piano learners are children. I may be naive, but I honestly assumed more would have happened in the half century or so since I was little.
korg nanokey has been useful for some projects, but I struggled with hammerklavier
As is known ... with many things ... there are various available sizes to cater for the community, individuals etc. Customisation is even possible.
For piano ... unfortunately there is the cost, logistics, storage, business, etc considerations. If it were that easy a solution, then most people would be catered/accommodated for by now.
At a performance venue or competitions venue or music stores or warehouses, or piano lesson studios etc, they might need 3 sizes, and possible two of each (for each size) ... for backups.
But at least there are some people or companies having a go at addressing the situation. It's obviously not straight forward.
But if some people (producers/designers) can handle the cost ... then at least some people (buyers) will be able to have a different key-size piano ... relative to the currently common size that is. So ... storage room and costs. But - at first - those buyers will likely be the ones that can actually pay a relatively high price.
