Can I just sell my lyrics?

Yeah, the thing you need is proof of creation.

The reason envelopes don't work is because they only prove the date the envelope was carried, not the date of the contents. I have heard of cases where dated proof was accepted in court action - one I recall was a live performance of a song that was recorded for later television broadcast. The dated tape and station logs were accepted as proof of composition on or before the performance date.

But proof of composition is only half the battle in a copyright case. You have to also prove that the other party had access to your work... and that's tough. If you file for a formal copyright, that's considered 'constructive notice' - in other words, it's a matter of public record that you wrote it on or before the date you filed for copyright, and anyone searching the record could have come across your song. That places the burden of proof on them - they need to show how they came up with it independently.

If you have a notary public certify a date, you may have proof that you wrote it... but you now still have to prove the other person copied YOUR work, rather than independently coming up with the same idea. If you submitted a demo tape to the band's manager, and you did that by certified mail or some other 'signed for' delivery method, you might have a case. But if your song has been sitting in a desk drawer in Des Moines, you'll have a tough time convincing a jury that some L.A. band 'stole' your song - the jury is going to wonder how they could have!

Good point... This whole song writing thing is a mess. But thats why im taking business and law classes... heh.