On page 466 of the book, in the chapter called "The Mirror of Galadriel", after Frodo finished the song, this is what it says:
'Why, you'll be beating Mr. Bilbo next!' said Sam.
'No, I am afraid not,' said Bilbo [they meant Frodo!] 'but that is the best I can do yet.'
If you have not read the book, Bilbo is very good at making songs. Frodo made a song and Sam thought that he was better than Bilbo. Bilbo was in Rivendell at the time and they were in Lothlorien, so Bilbo wasn't even there. He meant to say Frodo instead of Bilbo.
You had to have read the book.