The weakness is, we need the internet to go online so we can hear the music (which we found on Youtube). What if we want to hear it on our music player without the capability of internet? That mean, if you want to hear it, you must download the music file.
I'll give you a trick how to download a Youtube's videos. Not only download, but convert it directly into MP3 file format into your harddrive. Go to your address bar browser and type this site's address: http://www.flvto.com/. Yes this site will give you some service to convert any Youtube's videos into MP3 format. Click some adds over there to give the site's developer some fund.
Open the newtab in your browser. Open Youtube site's and start searching the music video you like.
After found the music, copy the youtube's video link in the address bar. The link format would be like this (sample): http://www.youtube.com/watch?v=bO70EfNAG-U. Paste the link format into flvto area bar, which I give green circle mark on image sample below.
Once you klik convert to MP3 button, the progress bar will shown.
After the progress end, a download button will appear. Click it and save it to your computer hard drive.