You just can't really download mp3 music. What’s prevalent lately is that videos are downloaded from youtube in mp3 format. I don't know how regular it is, but it works. All you have to do is search on Google for "youtube mp3 download and throw out a lot of pages where you just need to insert a link to the youtube video and you can already download it in Mp3. Let's say there are a lot of fake pages. That's very good. I think it works: www.youtube-mp3.hu