Its a long shot but if you do not trust P2P (limewire etc) or bittorrent cause of viruses etc etc then use google or the YouTube hack i posted before in another thread... to Use google to search for Mp3s type the following into the Search Bar..
?intitle:index.of? mp3 "the name of artist or song" (without quotes)
Example if your looking for eminem type:
?intitle:index.of? mp3 eminem
Very old hack but still the decent one LOL
Hope you find what your looking for.....
P.S. you do get some strange advert ones but so becareful like i said its a long shot