There are two methods for this:

Method 1

1. First of all, look on YouTube the song you want to download, and copy the link in the link bar

2. Next, go to this site : YouTube to MP3 Converter - Video2mp3

3. Now, copy the link from YouTube to the "VideoURL" bar in the site, hit High Quality and click convert

4. After you wait a couple of seconds (or minutes depending on your connection), you click "download as mp3" or just wait 20 seconds.

Method 2

1. First you download this program "Any DVD Converter Professional", and then click on the YouTube icon, then paste the link from the video and hit OK (make sure the profile is selected as mp3)

2. Now click on the Convert icon and wait.

3. The default directory for stored downloads is C:\My Documents\Any DVD Converter Professional\MP3 (for downloads as mp3's)

or, if u use firefox, install a plugin like "Fast Video Download", u search and install on the PC a mp4 to mp3 convertor, u download with the plugin mp4 format and u convert it to mp3.
i use xilisoft.

NOTE:
if u have an audio sistem hi-fi, u might notice that the quality of the sound, on some youtube clips are bad, so if u switch it to mp3 u gone have the same bad quality.

There is also " youtube downloader " which is a free program that you can download off of cnet, it works pretty good and it always works.

or..

http://www.listentoyoutube.com/

Originally Posted by AlRah

or..

http://www.listentoyoutube.com/

yes, that's the most practical

Haha, I showed my friend this a few months back (He thinks everyone is out to get him). The only problem I have with this is the bitrates (which is maximum 128 kilobits/second). Thanks for posting this though...

i usually convert video to make mp3...its good techniques..

yea, i usually use other programs

you can use the aTube Catcher, but remember to put in MP3

havent tried this i will give it a go