P
ProVobis
Guest
Be careful here. Even if the music is in public domain, publications of same, such as Schirmer, are not. So individual copies must be bought for public use such as in Church.Most Gregorian chant is in the public domain (though not recordings of it) – it is simply too old to be under copyright protection.
For example, Corpus Christi Watershed cannot retain copyright of Adoro Te Devote, either the music or the text. Adoro Te Devote is in the public domain.
However, nowadays one get some midi and music software that can essentially print out public domain stuff.