One can also chord on conventional keyboards. A cheap keyboard with 2KRO (2-key rollover) and 4 modifiers, might be held upside-down, providing Shift/Ctrl/Alt/Meta plus a key or two. And a 2KRO with 8 modifiers (left and right aren't merged) might be used two handed. Some keyboards special-case common key sets like WASD. A 6KRO keyboard permits one-handed chording with arbitrary keys. USB boot-mode keyboards are limited to 6KRO plus 8 modifiers. :/ Full n-key rollover (NKRO) USB HID keyboards exist, but last I looked some years ago, it was a niche mess.

A half-century on, an we still can't play keyboards like pianos... "if your customers aren't complaining loudly of being crippled, you're overbuilding".

Perhaps its overkill, but I've always wanted to see more UI's re-purposing midi controllers (which certainly reproduce chorded functionality!):

https://www.amazon.com/Korg-NANOKEY2BK-Slim-Line-Keyboard-Bl...

https://www.amazon.com/Korg-nanoKEY-Bluetooth-Keyboard-Contr...

Somebody sent me this link: https://www.youtube.com/watch?v=8za_4g5zCOM -- sure, not the same, but somewhat related. I guess there are people at the Doug Engelbart Institute who know more and better chorded keyboard offers. At one point, there was work going on to produce them again, related to the HyperScope project.

Corsair has a mouse with a keyboard built-in that could be used for the same things. Even though I have one, find I just use Ctrl keys like everyone else. https://www.corsair.com/us/en/Color/scimitar-pro-config/p/CH...

There's this one https://twiddler.tekgear.com (not cheap though)

Bill Buxton's chording keyboard collection: https://www.microsoft.com/buxtoncollection/type.aspx?t=Chord...

There is the Tap[1] which is not only a chord keyboard, but a really neat piece of wearable hardware.

[1] https://www.tapwithus.com/

I use a ErgoDox with a custom layout which uses chords for programming symbols.