Is he being purposefully obtuse here? Seems likely. I mean, a) using the French for song, a form that is usually secular then b) making that song Pious – It’s just – well, we expect a pious hymn or a pious chorale but a pious chanson? It’s like a pious pop song – not unheard of but still pretty weird.
Then – the first row? Is he saying the first line? The first verse? Or is this an accepted way of talking about music in Renaissance England (or Pre-Denmark pre-Renaissance)? The first bars on a sheet of music might well be called a row; there is a row-like appearance.
This is where music scholarship and literature scholarship might get together and have a conversation. Hell, I know a music scholar, maybe I’ll ask him.