Crossfader not working in Rekordbox 5 without controller connected?

Is this normal?  Will it work with a controller connected?  I'm very new to Pioneer and am just trying out Rekordbox 5 (I have a controller on order).  When I move the crossfader with the mouse it has no effect at all - I have to use the individual faders on the screen for the 2 channels - the crossfader all the way to the left does not silence the music on deck 2.  I am just currently playing the output through the speakers on my Mac.