Which version of Music Maker?

I think the issue is now you have the correct input coming from the keys to the program using the ASIO, but now the output needs to goto a synthesizer or wavetable.

See if in the dialog for the MIDI (I think that is found when pressing Y on the computer keyboard with Music Maker is open - select the Audio/MIDI tab and look to see what the output source is for the MIDI. There should be a drop down window. This would show you what your system has available. You should have something wither called Wavetable or Microsoft Synth... select, save and exit the dialog and try using the keys again in a MIDI project.