Stuart and Sons, a boutique piano manufacturer in Australia, made a piano with 108 keys: https://www.stuartandsons.com/108keys.html https://www.stuartandsons.c

Stuart and Sons, a boutique piano manufacturer in Australia, made a piano with 108 keys: https://www.stuartandsons.com/108keys.html https://www.stuartandsons.com/108keys.html They have an elaborate explanation of why they did it, and they are a commercial outfit, but the basic reason still seems to be "we wanted to see if we could".