I have audio that is being sent to my MBP through an audio in line that I would like to monitor for audio quality. The only way I know how to listen in real time to the audio is by way of Audio Recorder, but it seems a little unnecessary to have a recording application open simply to listen to my media that is being sent in. Is there a feature already part of OS X that allows me to turn this on? I looked in system prefs, but couldn't find anything to enable this. I will resort to audio recorder if I have to, but would be very happy if this was already a feature.