There is so much misinformation around about copyright and I've always been told that as soon as a work is created, the composer owns the copyright and you don't need to pay to acquire that ownership. I'm a member of SOCAN and I figure anyone writing music should be a member of their national rights organization and anything I write is listed with SOCAN.
I do not know how copyright laws differ between Canada and the USA but here's a summary for Canadian music from the Canadian Songwriters Assoc:
"Copyright is automatically acquired from the moment of creation of a work, provided that the work meets these three criteria: 1) the work must be original;2) it must be fixed in a somewhat permanent material form; and 3) the author must meet the qualified person requirements set out in the Copyright Act. A qualified person includes Canadian citizens and persons ordinarily resident in Canada. “Original” means that: 1) the work can’t be a substantial copy of another copyright protected work; and 2) the work must have been created by exercising “skill and judgement”, meaning it can’t be the product of a purely mindless mechanical exercise. See also 5.1,(qualified persons), 2.2. (originality), 2.3 (fixation) and 3.1 (registration).
The threshold test for determining whether there is an original work for copyright purposes is relatively low. The work has to be “non-trivial”, meaning it must meet a minimal level of creativity. For example, you can’t change two notes in a pre-existing song and claim it is a new and original work. However, many musical compositions follow a similar popular structure and rhythmic pattern and western music is bound by the limits of the 12 notes of the chromatic scale but the threshold can still be met- musical works needn’t be novel to acquire copyright protection.
There is no requirement that one register one’s copyright in order to acquire copyright. Copyright is automatically acquired from the moment of creation of an original work. That being said, many regard it prudent to register, copyright to their work with the Copyright Office as proof of ownership."
The above quote is from -
http://www.songwriters.ca/copyright101.aspx