How to Download YouTube Videos: 1. Go to video page. 2. Type "pwn" immediately in front of "youtube" in the url and hit enter. 3. Choose how you want to download the video (or even just the audio). No software, no gimmicks. Definitely one of the most useful and easy-to-use tools I've ever learned about.
Not sure that there really is a 'legal' way to download music without paying for it. Unless you go to bandcamp and an artist has a pay what you want that starts at $0. http://bythebirch.bandcamp.com/releases