How to download?
Install Mozilla Firefox as your web browser.
Install add-on "downloadhelper"
Get Foobar2000 and install it.
Just Google for these programs. They are all free and good, once operative.
Then, use downloadhelper in Firefox (add-on) to download a clip, as mp4.
You can watch those mp4's (or flv's) on the VLC player.
Download VideoLAN's VLC multimedia player from here:
http://www.videolan.org/vlc/
It's free; it has all the proper codecs for almost every audio and video format; there are versions for Windows, Mac OS X, BeOS, and Linux; and it will play just about anything.
If you want the audio only, get the mp4 as described above.
Play in Foobar, right click convert to wav.
You can burn wavs to audio cd's with NERO.
Or convert to mp3 as you see fit.
Always try to work with the highest resolution offered because hi-res goes hand-in-hand with higher quality sound reproduction on YT.
Good luck!