prisoner is being crucified, the priests  are singing the hymn "Pange, lingua, gloriosi" by Thomas Aquinas  (1264). However, they are singing a German version of this song,  which was not in use before 1969. In addition, even if they happened  to know a German version, it would be more likely for them to sing  the original Latin version, as there were priests from all over  Europe imprisoned in this block.