Producers copyright every one of your instrumentals before you even let anyone hear them. When you get in the habit of copyrighting all of your work you will always have some since of security knowing that your instrumentals are protected by the United States Copyright Office. That is one less thing you have to think about while you are focusing on being creative.
Simply put, copyrighting your music is to easy and non expensive to not do. For 55 dollars you can use the electronic Copyright Office (eCO) to upload up to 170mb of beats in a .zip file (128kbps/.mp3).
There are a lot of sites that have a copyright service but the only way to go as far as i am concerned is through the United Sates Copyright Office. But you are not done after that, read my article on tagging your beats.
After you copyright your beats. You need a good contract/agreement for your beats check out mine here.