Recording

Ok, so I want to get the audio from my cousin's video, and I want to be able to record what the computer is playing. Not what comes out of the speakers, but the audio that the computer is playing. Sort of like how you can take a snapshot of what is on the screen, but with audio. It's kind of hard to explain, so hopefully someone knows what I'm trying to do

It sounds like you want to extract the audio tracks from movies?

Yes that, and there are also tracks from Disney parks and other things that I want to get the audio but can't download it, and when I record it with a microphone it sounds terrible

If you want to pay for something, get Audio Hijack or Wiretap Studio.

If you want something that's free (but a bit tricky to set up), get Soundflower. That'll do the audio capture for you.

Also, I think Handbrake and/or Toast will extract audio for you.