For my build, I used counter sunk lag bolts to connect hockey pucks to the base of the cabinet and then put adhesive felt pads on the bottom of the pucks. It slides nicely and doesn't scratch, but the weight of it keeps it in place when playing.
For my piano, I use furniture sliders which are smooth plastic discs with a cup in the top where the wheels fit.
In most hardware stores you can get casters of varying sizes with a grey, non-marking rubber. It is softer for exactly your purpose.