You will need to install a user script manager extension to install this script.
Lossless, high quality YouTube download and MP3 converter.
The script works in:
High quality MP3s Audio is extracted from top quality video using lossless converter, it can't be better!
Real-time recording No wait - downloads start immediately.
Video recording in multiple formats Record your favorite videos as MP4s, MP3s, FLVs or 3GPs.
Script is based on youtubemp3script.com