If you and your friend wrote some tunes, then the two of you own the copyrights to those tunes, unless you composed the tunes as works "for hire." In that case, the copyrights belong to the person or persons who hired you. In the USA, the US Copyright Office does not issue copyrights in the sense that the US Patent Office issues patents. What the US Copyright Office does is register claims. Registering your claim may be a good idea depending upon your particular circumstances, but it is not the act which bestows the copyrights upon you. Authorship is!

--- Steve