Running one synthesizer through another as a line-in

[somethingillremember]

I posted this question on Yahoo Answers, shortly before realizing that nobody was going to answer it, so I thought I'd post it here to see if I got better results. Here's my question:

So I have a free Audio Unit synthesizer on Garageband called Automat, which is really nice for wave manipulation (good delays, modulation, etc.), but the oscillator waves and the samples it gives you to do stuff with really suck. Another free synthesizer I have, Crystal, is just the opposite. It has good samples and wave generators, but its interface is really annoying, and it's harder to work with. Automat, however, has an option for its oscillators called "linein", which I'm guessing means you can run another track or sound through the synthesizer. So I was wondering, is it possible to run Crystal in one track, and run Automat in another track and have Crystal running as a line-in through Automat? And can you do this while simultaneously muting Crystal's track?