On page 82 of volume 2 of The Psalms in Israel's Worship, Sigmund Mowinckel states:
"We have evidence also of the existence of strained and antagonistic relations between singers and priests. It seems as if the singers considered their own part in the temple service to be just as important and essential and that of the priests, and claimed that this fact should find expression in the hierarchic precedence code. We find manifestations of this in legends as well as in historical testimonies. In one version of the story about Korah, put together in Num. 16, the priestly story-teller denounces the sons of Korah because they aspired to priesthood and wanted to obtain control of the offering of incense; but, as we shall see below, the sons of Korah represented the temple singers."
And there are Psalms that are for the Korahites---42, 44-45, 46-49, 84-85, 87-88. When I was studying the Book of Numbers for my weekly quiet time, I think I heard or read religious interpreters who said that the Korahites redeemed themselves, in a sense: they were rebellious, but they eventually became temple singers. But Mowinckel says that there was rivalry between the priests and the temple singers, such as the Korahites. Could this be why there are Psalms that criticize sacrifice, such as Psalms 50-51?