There seems to be a problem with the mouse piano
A quick hint from codeweavers support:
you might try installing the "Platform SDK Redistributable: GDI+"
package into the same bottle as capella. You'll find this package in
the "Community supported applications" section of Crossover's
Install Software menu. In my own testing this enabled the keyboad,
but clicking on it cause some kind of catastrophic freeze that I
haven't yet been able to figure out. Hopefully this will help point
you in the right direction.
However, as I don't use the keyboard (and I'm a simple user, but no betatesting maniac), I won't even give it a try. Whoever finds a solution (which means, without "catastrophic freeze", of course) is welcome.