Just search torrents on the first link provided, and use the second tool provided to download, extract, and place on your Mp3 player. To get an entire artist's body of work, search "(Artist Name) Discography".
If you want to download from youtube just use aTube Catcher. It's a software to be downloaded but you can download videos anyhow you want. HD, MP3, MP4 etc etc you have around 40 options to choose from.