Lezioni private AKA Private Lessons (1975) - Vittorio De Sisti

Trama: Il diciottenne Alessandro, iscritto al conservatorio, è interessato più alla musica che al sesso. Ne insidieranno la virtù la vivace coetanea Emanuela, il di lei fratello gay Gabriele, una servetta di casa e perfino la nuova insegnante di piano.

A sexy piano teacher is the object of desire of one of the young boys in her class. One of his classmates finds out where she lives and hides outside her place, taking pictures of her undressing and writhing naked on her bed. He uses those photos to blackmail her into dressing up and acting like a hooker while teaching the class, and from there things get interesting.

Quando l'amore e sensualità AKA When Love Is Lust (1973) - Vittorio De Sisti

Synopsis:
'A young girl marries a handsome and successful but brutish local butcher at the behest of her contessa stepmother. The new wife turns out to be frigid on their wedding night, and the couple have a big fight. The wife goes out of town to stay with her older, married sister and gets involved with her sister's jaded swinger friends. The husband consoles himself by picking up prostitutes and carrying on with a sexy, voluptuous neighbor right in his new mother-in-law's villa. For some reason the mother-in-law considers this a turn-on and becomes sexually drawn to her loutish son-in-law...'
- lazarillo (IMDb)