Many people are looking for software or online tools that convert youtube movies to mp3. You can find a lot of software on the internet but be careful with this (adware, spyware, viruses,…).
Some websites can convert the youtube video online without installing any software. I’ve used different kind of tools and most of them complains every time about old java versions, needs to be updated,… A pain in the a** for people with basic knowledge of computers. I’ve found a very handy tool here: http://www.youtube-mp3.org/
Just enter the youtube url, click on convert, et voila! Nothing as easy as this website!