Flying by the seat of my pants, have great gear but non matching skill, trying my hand at computer recording, using garageband but want to record live instruments, track by track, want to use a mixer but have a imac (flatscreen) and a new emac and can not figure out how to connect a mixer to it? are there any usb one's (I have a Pod xt for guitars, its for the microphome inputs. influences=all genres but rap