Keepvid Stream - it is a free online service to convert videos from YouTube to mp3 format for free. You can get mp3 in different bitrates: 64kb, 128kb, 192kb, 256kb, or the best quality - 320kb.

4 simple steps to download mp3 from YouTube:
  1. Enter a valid url of video on the YouTube website.
  2. Choose MP3 Bitrate to convert to.
  3. Press the button "Get mp3!" and wait a little time until the end video conversion.
  4. Download mp3 file. That's all!