Very easy steps using a Windows PC:

  1. Download VLC Player
  2. Get  the YouTube video URL
  3. Open VLC. On Windows, go to Media > Open Network Stream (On Mac go to File > Open Network.)
  4. Enter the Youtube URL
  5. Click Play
  6. While the video is still playing, go to Windows go to Tools > Code Information
  7. A new window will popup, look at the bottom there’s a long address in the Location field. Copy that and close window.
  8. Stop the video
  9. Again, Go to Media > Open Network Stream.
  10. Paste the long address in the network URL field.
  11. Click on the down arrow next to the Play button
  12. click on Convert.
  13. click on the Profile drop-down menu
  14. select Audio – MP3.
  15. Click on the Browse button next to the Destination file: Select the desitination folder where you want to save the mp3 file.
  16. Click Start.
  17. Look in the folder where you selected for the destination file.
  18. Enjoy