I don't quite understand your question or your situation. What ort of society is this, why do you want to join, and what will it do for you? What is the exact requirement? I think you may be confusing legal terms. "Fictitious name" is different from a "trademark" or even other things. Please try to explain better.
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You most likely are referring to BMI or ASCAP - competing organizations that register / copyright / license art rights, in exchange for a percentage of royalties, of course.
An interesting, but rather one-sided analysis of the two organization can be found at : http://home.earthlink.net/~deankay/TheBigDifference.html
Having a music label / publisher is important because they have the organization and capital to promote your music.
Simple answer - - you really need to make an appointment with an experienced entertainment lawyer. There are many fairly complicated issues and contracts involved. In this person's humble opinion, you need representation.
Any response does not create an attorney - client relationship without both parties fully signing a representation agreement.