In this tutorial I will show you an ABSOLUTELY FREE way to record the system audio from your computer (not microphone) using Quicktime and a free program called Soundflower. This is useful for screen recordings that you need to capture your computer's audio with, or legally recording uncopyrighted audio. So let's take a look...
(I'm not as familiar with WIndows computers, but I believe there is another program called "Jack" that should do pretty much the same thing. But I'm not 100% sure.)
Step 1: System Preferences
If you notice, there's nothing in the input about receiving the computer audio, and nothing in the output about outputting the computer audio. But don't worry, we can fix that.