Pies Iesu Domine,
Dona Eis Requiem.
The chant, the monks were saying during the 'Bring Out Your Dead' segment of Monty Python And The Holy Grail.
It's actually the last two lines of Dies Irae (Mozart's "Requiem Mass in D minor")
("Kind Lord Jesus, grant them rest").
MPATHG, Python (Monty) LLC