Caution, pyNaps has been created to download free music, but it can download protected musics by copyrights. The download of theses musics is illegale, and I reject any responsibility of your acts. And I haven't found a technology to filter this protected music to the free music.
pyNaps is a free open sources software for music downloading under GNU/GPL license
It can search, and download music.
It's a Direct Downloading software, so it doesn't require any firewall configuration. It's really easy to use.
pyNaps is in a beta version, and have not already any package, so see the installation page.