Is it within the guideline to upload new versions of out-of-copyright compositions? For example, a new recordiing of a Mozart piano sonata or Renaissance Mass, etc? To be clear, the music would be newly arranged and performed.
According to Berne Convention for the Protection of Literary and Artistic Works, the general rule is that protection must be granted until the expiration of the 50th year after the author’s death while it might be possible that the copyright is inherited by his descendants.
But most works are public copyrighted at that time, it will not become a copyright issue as long as you could make sure it is public copyrighted and don’t adopt the recording of others.
Hope that helps.