1) Do you want to plug the Line Out of some other audio device into your Mac's Line In socket and record that in GarageBand: answer = yes you can
2) Do you want to record what's coming out of the Line Out socket on your Mac, using GarageBand on the same Mac: answer = don't think you can with GarageBand, but you can using Audio Hijack
I want to record music from a website, but hate recording using the mic as it's too quiet. I want something which will record what is coming out of the speakers at the same quality.
I want to record music from a website, but hate recording using the mic as it's too quiet. I want something which will record what is coming out of the speakers at the same quality.