Ikebe Shinichiro - D-ZAKA NO SATSUJIN JIKEN / The D-street Murder Case (jap, Jissoji, 1998)

Is that a real theremin? Sure sounds like. Very effective unsettling OST about which I could find no details online. The film is a typical Rampo story with foreboding replacing mystery, repressed obsession and perversity present and correct, directed with slick and measured control by Jissoji Akio, he of the Buddhist trilogy (70-72) but also Ultraman. 

four tracks here