Except that those predate the era of music records. People are not interested in notes, they are interested in the music. Recordings of Bach and Vivaldi are still usually not in the public domain.
Yes. However, if the music is out of copyright that creates a free market in recordings of the music so it leads to there being budget recordings available.
Personally I am interested in the notes, so I'll point out that most of the sheet music for Bach and Vivaldi is in fact under copyright. If you want something out of copyright then you have to get a facsimile of an old edition. Or something that was typeset by an amateur, which will almost certainly be crap because typesetting music takes a lot of skill to do well.
Maybe most baroque recordings are not public domain. But you can find many good-quality recordings of any particular piece under reasonable creative commons licenses [1].
> Even the sheet music is still copyrighted, because you want modern notation, not photographs of the originals.
And you can very easily find them.
Most moderately well-known compositions have been transcribed into pdf using modern typography (say, with lilypond) and uploaded to imslp and similar sites.
This is already the case for most of the music that many people are interested in (e.g., Bach, Vivaldi).