Flv is a video format, as you probably know. You can do it from the
commandline using mencoder. I think that Sound Converter in the repositories
can handle the conversion to mp3 then you will be able to make an audio CD
using K3B or similar application. Both are in the repos.

www.linuxquestions.org/.../copy-mode-extract-of-au\
dio-from-youtube-flv-video-508026/