Motet

[Terence Kelly]

I bought a used LP at a tag sale that had Sacred works by Nanino and the "Venetian School" of late Renaissance composers.  One Motet was by Giovanni Matteo Asola called "Cantabant Sancti".  The last words at the end are sung "voces corum".  It's printed that way on the album cover.  I thought it should be "voces eorum".  I also found a book of Asola's works and "Cantabant Sancti" was included.  That edition also had "voces corum" printed.  I couldn't find "corum" in my dictionary under anything that looked like a nominative.  I can't believe a mistake like that has survived over 400 years without ANYONE saying ANYTHING.  Any thoughts?