I own a Macbook Pro (Late 2008, with input). I am teaching guitar lessons over Skype and I would like to know how I can talk into my Microphone while having my electric guitar plugged in to the input so the person on the other end of the chat can hear both my voice and the guitar. Right now, I can only either choose my microphone or guitar input. Plugging my guitar through an amplifier is not possible for me. Thanks.