Hi, Ive been wanting to record some friends during their live shows. Im completely new and have no idea how to start. They already have a mixer and and am not sure if i need something like icontrol or mobilepre usb. I do have some griffin cables that connect to my macbook and have the other end to connnect to guitar or mic. Is there a way just to connect my macbook to their mixer and record or should i buy one of these other products?