In this post, I will talk about Sigmund Mowinckel's discussion on Psalm 50 on pages 68-73 of The Psalms in Israel's Worship, Volume 2.
Ordinarily, Mowinckel disagrees with the scholarly view that the classical prophets influenced many of the Psalms, which the scholars Mowinckel disputes date to the post-exilic period. Mowinckel thinks that, on the contrary, the cult contained elements that influenced the classical prophets, which should not be surprising, considering that "the beginning of a 'prophetic' element belonged to the cultic order itself, and...it was out of the latter that important ideas in the classical prophetic movement sprang out and grew" (page 69). Mowinckel often emphasizes the new year festival as the setting for many Psalms. At the new year festival, creation was preserved from the attacks of chaos, so that Israel could have a prosperous new year. Elements of the new year festival included God epiphany, as well as an acknowledgment on the part of the Israelites that their prosperity was contingent on their moral behavior.
Psalm 50 has these sorts of elements: God makes an epiphany, and there is an acknowledgment of the importance of morality, as Israel is criticized for theft, adultery, and slander (which Mowinckel interprets to be sorcery). Mowinckel says that a cultic prophet preached "the chastising and admonitory word of Yahweh" (page 70). But, in this case, Mowinckel believes that the reform prophets had an influence on the cult prophets. The reform prophets had a derogatory view of sacrifice, emphasizing instead "the right fundamental relationship to God in faith and obedience and the social ethic" (page 70). In Psalm 50, however, the cultic prophet elevates "the offering up of praise and worship, the thanksgiving psalm and the penitential prayer" (page 70). For Mowinkel, Psalm 50 grew out of the cultic religion---which had a Torah liturgy that prescribed moral requirements for worship (Psalm 13:2)---but it was also "stimulated...by the prophetic movement" (page 71). What's going on in Psalm 50, according to Mowinckel (if I'm understanding him correctly), is a combination of the cultic prophets' view on the importance of thanksgiving, with the reform prophets' emphasis on morality.
But Psalm 50 is not as gloomy as the reform prophets, who depict God coming to annihilate sinners. Rather, in Psalm 50, God comes and rebukes Israel (though I must note that v 22 threatens annihilation). According to Mowinckel, we see here "the toning down of the fiery moral preaching of the prophetic movement which took place during the development of the Jewish 'religion of the law'", beginning in the Persian Period. So Mowinckel views Psalm 50 as an exception to his rule that the Psalms influenced classical prophecy, rather than the other way around. And Mowinckel dates Psalm 50 to the post-exilic period.
I've been looking at these pages of Mowinckel over and over, trying to make sense of them. I guess what he's saying is that the reform prophets influenced Psalm 50 in terms of its criticism of sacrifice, as well as its moral rebuke of Israel. Other Psalms may presume that Israel should be moral, but they usually don't rebuke Israel in the second person, as the reform prophets did, and as Psalm 50 does. But Psalm 50 adds a cultic spin onto the anti-sacrifice theme by emphasizing thanksgiving and praise.