One of a Kind (1976)

"CAUTION: This Film Contains Strongly Erotic Musical Powers"

A man happens to buy a very special accordion. Its music makes any woman incredibly horny and lustful, makes her forget about everything and just yield to temptation, no matter what. Maybe this is hard to believe, but as soon as the new accordion owner tried it out he knew it was true. His fiancee was the first to lose her mind, then her friends experienced the magic of the accordion, and that was only the beginning.