Unfortunately, GarageBand for the Mac can't create a file that can be used on the iPad. The transfer only works one way from the iPad to the Mac and only with the very latest version of GarageBand. Just as an update brought about that transfer, I'm hoping that we will eventually get an update that will work both ways.
After updating GarageBand yesterday, I thought this problem would be solved. It seems as though, only half the problem has been rectified.
I can transfer a project from my iPad2 to my Mac, but after editing and transferring the same project back to my iPad... no luck.
Emphasizing this so much at the Keynote, you'd think Apple would have the accessibility in place to do this. We've waited until yesterday to have this problem fixed, and they've only fixed half the problem.
We'll get there eventually - I'll just have to wait.
You might try posting your GarageBand for iPad specific questions to that forum (it is separate from here). Link to forum: http://discussions.apple.com/forum.jspa?forumID=1438
There are a couple of threads, one with specifics - on how to transfer GarageBand files back and forth between the Mac and the iPad versions of GarageBand. Here is one link: http://discussions.apple.com/thread.jspa?threadID=2784430&tstart=0
thanks for these links but Apple "upgraded" their forums over the weekend, making everything look like cartoons with word ballons for posts. They also moved, combined, and deleted several forums so now pretty much every existing GarageBand iPad thread link is broken.
Hopefully they'll fix this and your informative links will work again.