Logical inconsistency 2.0
Attention must be drawn between the *text* contained within a book and an *imprint* thereof. The works of William Shakespeare are sufficiently old to be public-domain, but you'd still expect to pay for a printed copy because of the effort that's been vested in producing the layout, pagination, choice of fonts, binding etc.
The printed copy is copyright; the actual *words* contained therein are PD.
Same goes for sheet-music: the works of Beethoven Bach and Thomas Tallis are in the public domain but the likes of Boosey & Hawkes will still come after you if you photocopy their copyrighted sheet-music imprint.
The printed copy of the score is copyright, the *notes* in Spem in Alium aren't.