“Polyphonic Credo” during Communion?

It sounds strange to Americans, but a very common European tradition is to sing a polyphonic “Agnus Dei” during the distribution of Holy Communion, famously defended by Cardinal Ratzinger in 1995. Monsignor Francis P. Schmitt wrote about visiting Saint Joseph Oratory in Montreal, and says: “A polyphonic Creed was sung during the distribution of Communion.” In my humble opinion, that seems a bit strange.