This was a European Vintage Classic (not too old) full movie on a DVD. The plot was something like a shy woman peeps into other people windows and sees different type sexual encounters. One of the scenes I remember vividly included 2 naked women walking on a road at night, meet with a man in car. He invites them in his car and they do the deed (FFM) in the backseat while the driver drives the car. Another scene included 2 women dressed in stockings and corset(European style fashion), entering a fancy room where a man was playing piano. They (FFM) get on the piano and use a champagne to drip over each other's genitals and get on with the deed. In the ending scene, the women peeping was found by the people and was also invited to a room with handful of men and now 2 women.

Please let me know if this ring any bell in your mind. I watched it in 2011 I believe and the quality of the film was clear. I believe it wasn't older than 80s.