alt Hacker NewsMy copy of "Sense and Sensibility and Sea Monsters" is explicitly listed as being copyrighted by Ben H. Winters in 2009 despite the majority of the words being Austen's, though. Perhaps music has different rules compared to text. I suspect Winters and his publisher have investigated the legality of this more than either of us have.
Jane Austen died long enough ago that her works are in the public domain, so Winters did not need a license to use it. That does not mean that he gained rights to her work: if he tried to sue someone for use of anything which appeared in the original, he would lose in court because it’s easy to show that copies made before he was born had the same text. This also how they prevent people trying to extend copyright by making minor changes to an existing work: the new copyright only covers the additions.
There’s a very accessible summary of the United States rules here:
https://www.copyright.gov/circs/circ14.pdf