by markbrai » Mon May 18, 2009 3:19 pm
The answer is yes you can, but it requires some "creative" routing. I'm only a new RiffWorks user myself but was playing around the other day with the same situation you are and came up with this which seems to work.
Basically, RiffWorks only recognises a signal through one of the inputs in the audio setup menu. So the answer is that somehow you have to get the audio from GarageBand into one of those inputs.
If you have an external audio interface then this is very straightforward. Set the input and output of Riffworks to the audio interface. Then set the ouput of garageband as your macs line out. Then connect the line out of your mac to the line in on the interface. Finally connect your headphones/monitors to the interface outputs. There we go, RiffWorks will now "hear" the keyboard being played through GarageBand.
If you don't have an audio interface, then I think there might be a software way of doing a similar thing, but not 100% sure. Hopefully a more experienced user will be able to clarify this as I'm sure the question is posed fairly frequently!
Hope that helps!