Because classical songs are so old, many of them are in public domain. (Okay, I don't think that's true, but go with me here.) And because classical music makes you a smarter person and potentially makes the child in your stomach smarter, you should always listen to classical music.

I've always heard friends complaining that they would be smarter if they knew where to get some good classical. You can't really ourTunes the network for classical music. Thankfully, Wikipedia has an excellent compilation of music in the public domain.

Give your hears some bliss and get better grades: Wikipedia:Sound/list