Electro-capacitive boards (EC) could also do this, with the caveat that EC switches in general are tactile rather than linear as most hall-effect (HE) switches are.
When it comes to QMK, it seems that there is a greater number of EC keyboard projects out there. Some examples below.
For a MIDI device, I imagine an ortholinear boards may be the best layout. Unfortunately there isn't much out there for EC ortholinear boards. A group buy for a 47-key EC ortho board ran a few years ago, but the price was an outrageous $500-600:
More recently, a handful of QMK-compatible EC PCBs have popped up on AliExpress. Unfortunately, I haven't been able to locate the actual QMK firmware source for them. Perhaps in the minds of the creators, it is simply enough to provide VIAL compatibility for user customization. The drawback here is it does not expose the necessary feedback for velocity:
When it comes to QMK, it seems that there is a greater number of EC keyboard projects out there. Some examples below.
For a MIDI device, I imagine an ortholinear boards may be the best layout. Unfortunately there isn't much out there for EC ortholinear boards. A group buy for a 47-key EC ortho board ran a few years ago, but the price was an outrageous $500-600:
https://www.ashkeebs.com/product/conundrum/
More recently, a handful of QMK-compatible EC PCBs have popped up on AliExpress. Unfortunately, I haven't been able to locate the actual QMK firmware source for them. Perhaps in the minds of the creators, it is simply enough to provide VIAL compatibility for user customization. The drawback here is it does not expose the necessary feedback for velocity:
https://www.aliexpress.us/item/3256806073672667.html
https://www.aliexpress.us/item/3256806010654548.html
https://www.aliexpress.us/item/3256806009306496.html
https://www.aliexpress.us/item/3256805431878689.html