Deo gratias (‘thanks to God’) by Johannes Ockeghem (1410/30-1497).
This song is made up of 4 overlapping canons, each for 9 voices, so a 36-part canon. Every bar a new voice starts, starting with the sopranos and then going on with altos, tenors and basses. All of these 4 voices thus need 9 singers.
The sopranos sing Deo gratias 6 times, the altos 4 times (with 2 extra gratias added to the 3rd), the tenors 9 times and the basses sing it 5 times. So the sopranos sing Deo gratias 54 times, the altos 36 times, the tenors 81 times and the basses 45 times. That makes a total of 216 Deo gratias.
The correct Latin by the way is not Deo gratia, as printed in some scores, but Deo gratias. As the phrase is derived from Deo agimus gratias (‘let us give thanks to God’) the word for ‘thanks’ must be in the accusative, which is gratias in the plural and gratiam in the singular.