This is an outstanding film -- probably my favourite -- and one of the things that puts it over-the-top is its soundtrack. In particular, a drums and electric guitar bit that surfaces during the first hardcore seduction scene. It figures prominately on the dvd menu. Plus the dvd has an "isolated score" feature, so you can listen to it exclusively.
The film is definitely a product of the 70s when porn producers did something unusual -- they told a story.