I was talking to my son-in-law, who wrote his PhD thesis on copyright, about my visit to the Library of Congress and two questions I had there:
1. What is the difference between the card catalog of more official looking cards with song titles and the "Claimants" section where there are pink slips, not cards?
2. Why do we find different people copyrighting the same song?
He said that the "claimant" slips are for songs people laid claim to without having sent actual paper sheet music of any kind to the office. He also said that, unlike the Patent Office, the Copyright Office never investigated claims. If you send in your paperwork, you got the copyright you asked for; if somebody else sent in the same song, they got the copyright too. It wouldn't matter until somebody sued.
For that matter, I was reminded you don't actually have to send paper anywhere, your song is implicitly copyrighted. However, if it comes to a law suit, you'll wish you had.
See here one of the Zhelonek songs, "Tsirele Mirele" or "Zirele Mirele" or "Cirele Mirele" (depending on the transcriber), as it was sent to the U.S. Copyright Office by Aaron Lebedeff in 1927.
I was told by Henry Sapoznik that Lebedeff did not write this song, he says: "The title is not in the Heskes book under Lebbie's name but the title turns up on a UHD&C [United Hebrew Disc and Cylinder Company] disc from about 1905 with no composer credit. And yes, it was neither uncommon for artists to claim authorship for things they did not write as much as it was common for composers to fail to submit copyright papers for things they did write."
It would be interesting to hear the 1905 version. What I do know is that this scrap of handwritten music from the copyright office is only about half of the melody as Lebedeff himself recorded it, and it's in fact missing the entire section which one would call the "hook" of the song. What a mystery.