In the case of classical music, there are two things that need to be clarified:
1) Classical music is still being composed today, and there’s a huge volume of post-1927 work that is very much under copyright in the US (excessive though that may be IMO).
2) Even if a composition is PD, the recording is absolutely copyrightable if it’s post-1927, and the arrangement may be as well. This isn’t a matter of confusion; it’s an actual piece of intellectual property.
Not to say that any of this is right; I believe fair use protections need to go much, much farther than they do.