I immediately think of the obscure score for 'Utamaro's world' (Utamaro yume to shiriseba) from 1977 in the 'pinku' genre. The music by Ryohei Hirose is wonderful, sensual, witty, beautiful and sexy. Everything this sort of movie asks for. My friend Yasuhiro Wada (re-)released this on LP back in the day as the very first Soundtrack Listeners Club title.
The rest of the top ten would be filled by Morricone scores, like La Venexiana, Dedicato al mare Egeo etc. And Caligula (Isis Pool!) by Bruno Nicolai, errr sorry, Paul Clemente. Oh, and Justine by Nicolai, of course. Sesso Matto by Trovaioli, does that count? I guess it does! So does Lulu by Chiaramello. All top ten PORN scores to me.