YouTube has been around a long time. I am just now learning how to grab the audio part of a YouTube video so I can play it on my computer or iPad. I do not profess to be smart about this subject, but for my own memories sake, and because I like to share, here is what I have found.
There are 2 websites that will grab the sound file for you and then download it to your computer as a MP3 file. They are Peggo and TheYouMP3. Both work fine, are free, and do not require registration. I am not an expert on MP3 files, and so cannot tell if one site is producing higher quality than the other. But I have opted to use Peggo.
You do not need to install any software. Simply open both YouTube and the other site, say Peggo. Find the video you like, copy it’s URL and then paste it into Peggo. Then click the Download button, and in a few seconds you will have the MP3 file. Simple stuff.