I agree with Herb; copyright registration is a waste of money especially since most writers/musicians will be lucky to break even = earn zero $$$
Theft of a popular, finished and released recording by a major group, via illegal digital copying, is so common as to be approaching the worldwide norm in recording distribution. This type of theft results in billions of dollars in potential lost profits annually. Infringement of performance rights on a mega-hit via unlicensed covers is common enough, but in most such cases the damage is minimal. In the event that an unauthorized cover hits it big, it is not too difficult for the author to, locate the guilty party and extract damages. Outright theft of an author's basic composition, by stealing the unpublished work and claiming to be the true author is very rare. You hear about it only when the ownership of a mega-hit is in question and lawyers are willing to line up for a tasty contingency fee.
The main reason for that rarity, can be seen by a simple analogy. Most of us would not leave a pile of cash on the bench at the gym while we went to take a shower. Someone seeing it might be tempted to take something of such obvious value, and so easily fenced=spent, and might easily decide that the risk to value ratio for stealing it was acceptable. Were we to leave one of our beat-up running shoes on the bench, we would probably expect it to be there when we returned. It is pretty unlikely that anyone would be able to turn that shoe into something of value to them or a potential buyer. If we had to pay money to secure the shoe in a locker, it would probably be a wasted investment.
An unpublished work of art is more like the tennis shoe, than the cash. Yet many artists think of their work more on the analogy of a lottery ticket. If it is a losing ticket, then someone taking it would be a pretty stupid petty thief, but if it is a winner, they have made a fortune. The decision on how much effort to take to protect the lottery ticket before the drawing depends on the hope of the ticket holder.
If you believe that you are holding a winner, then certainly early registration of the copyright (where available) is a good choice for you. If it really clearly is a valuable creation then, someone who makes his living exploiting artists' work, will be able to deal with his qualms about not being able to file for the initial copyright registration himself. If his belief in the potential profitability of the copyrighted work is so low that he will be reluctant to buy it, then it is not too likely that he will expend a lot effort in promoting it anyway.