La Maison Des Phantasmes (1978)
Since Mathieu lost his virility in a car accident, he spends his days playing the piano in his luxurious country villa and arranging various sexual adventures in which his wife Clarisse reluctantly takes part. These also involve the girl, Emilie he is teaching to play the piano and her mother. And the maid and butler get in on the act too. One fine day, Clarisse is also sent am abandoned house to have sex and is attacked by three men- which is organized by her husband. She manages to escape, but they pursue her to her home. There, they rape and humiliate her under the eyes of Mathieu and the others. This turns into an orgy but her husband regains all his virility with this shock- as the doctors said before and takes her on the floor to the delight of everyone. The accomplices then slip away and leave the couple alone in the privacy of the half-light.