cd player, ipod etc. into your mac and use its’ speakers. This lets you listen to your ipod, radio or anything with a headphone jack using just the speakers your computer already has. Free Line In Software: www.macupdate.com -I did not make Line In, I am not responsible for the productivity of that software. … gabeabrams all about your mac into speakers ipod cd player radio line in cord headphones headphone help cool gadgets tech apple macintosh innovative free video fun interesting …