These forms are for registering two different types of copyrightable subject matter that may be embodied in a recording. Form PA is used for the registration of music and/or lyrics (as well as other works of the performing arts), even if your song is on a cassette. Form SR is used for registering the performance and production of a particular recording of sounds.
This article is intended to be helpful and informative. But even common legal matters can become complex and stressful. A qualified intellectual property lawyer can address your particular legal needs, explain the law, and represent you in court. Take the first step now and contact a local intellectual property attorney to discuss your specific legal situation.