Wiktionary
propers
Etymology 1 n. (plural of proper English) Etymology 2
n. (context slang English) proper treatment, respect
Usage examples of "propers".
We go to the eleven o'clock solemn High Mass, with plain-song propers sung by the Ritual Choir (that's Darcy Dwyer's lot) and a missa brevis and motet sung by the Gallery Choir, which is like angels, if angels can sing, which I suppose they do.