SR forms were invented for record companies, plain and simple.
If you want to know the truth, and I speak as someone who does copyright research for my steady income, SR registration is one of the least credible forms of documentation in this field - precisley because people think they are killing all the birds with one basket (Um, something like that) and they aren't. You have to make proper notes - and that is still not what the SR was made for - those addendums were made because of so many people using the wrong form - LOC was like "Well, if you are going to use the wrong form, you might as well use the wrong form correctly" even if it isn't correct. See what I mean?
Sure, if you have written and recorded an album, and you wrote every piece of music on the record, you can make that little note that the SR registration includes words & music, but that is still not what the form was intended for. There should be no confusion: use form PA to register a song, or a group of songs. Do a separate SR form to cover the album itself.
I think gec is getting the rights to master recordings confused with SR copyrights...
Rights to master recordings is something that is negotiated for in a record contract - and unless your shit is of the unstinking kind - just about everybody signs over the rights of master recordings to the label - it is just how it is done (this is why you hear about bands not wanting to release a greatest hits package, and then see it on the shelves anyway - that is the record company making some more green) Don Henley is in court right now fighting the terms of master ownership - making the masters property of the artist after a certain amount of time - whether the artist asks for it or not - blah blah blah...
Anyway, back to copyrights - I wish I could just write an end all statement that would convince y'all to use the PA form - but alas, there will be someone who wants to argue - and all I can say is go ahead and use SR if you want to. But that is not what it is for.
Use PA forms and make my job easier, please.
Brad