Piggybacking off of Tambay's review below about The Slender Thread... he mentions Quincy Jones' score for that film, as well he should have.
Back from the mid-1960's to the early 70's, Jones was quite a prolific film composer, writing scores for some of the most important films of the period, such as writer/director Richard Brooks' 1967 film adaptation of Truman Capote's In Cold Blood, The Hot Rock and Sam Peckinpah's original 1972 version of The Getaway.
But my favorite Jones film score was for the Sidney Lumet film The Deadly Affair (which is now available on Sony Home Video DVD-on-demand label Columbia Choice Collection) released back in 1966 (when they used to still make films for adults).
It was based on John Le Carre's first novel A Call for the Dead, which introduced his famous spy character George Smiley; though he's called Charles Dobbs in the film because another studio owned the rights to some other Le Carre novels, and even the Smiley name as well.
And the film, which is excellent by the way, with Lumet at the top of his game, actually plays like a test run for La Carre's later Smiley novel and film, Tinker Tailor Solider Spy, since they both share similar plot details.
But the score is one of Jones' best, with a distinctive jazzy bossa nova beat.
Take a listen: