Your best to purchase the song from their rightful owners. because in a few years when these websites get sued for copyright infringement the record labels will have full access to all the people that downloaded the illegal material. do you want to get sued for $3600 a song? think about it.
Downloading music in mosts cases will be illegal (some music is free)
I use
http://torrentz.com to search for various things (it's a search engine)
http://demonoid.com for more specialized searches (it's a private tracker, so there's usually harder to find things there)
check your emails, I sent you an invite to Demonoid