YMUSIC is a tool that you can use to play video from YouTube in the background and download video in various formats (including mp3)

Listening to music with YouTube with 90% saving traffic;
Listening in the background;
Quick switching with of. YouTube applications for playing in the background;
Quick download/listening to music from the YouTube application and browser through the "share"/"open"/"open";
Download video from YouTube in different permits, converting to mp3 320 kbps or webm, backgro