The Tale of the Dean’s Wife (1970) (1970)
A decadent professor of erotic studies and his wife arrive at the dean’s suburban home for a party. After a drink, the professor eagerly demonstrates his “pleasure through pain” theory on the dean’s willing wife. She lays down on the couch and he thrashes her vigorously with his belt. (Late-period nudies sometimes tossed in a bit of “roughie” style S&M.) Her masochistic response has an aphrodisiac effect on the professor’s wife and a lesbian sex scene follows.