It almost doesn't sound like a Henry Mancini score at first -- both the rousing, thunderous "Western action" intro music and the intentionally "tinny" version of Send a Little Love My Way don't sound like the Mancini of The Pink Panther and Moon River.
But he's there...he's noticeable if you really listen.
I do like how, in the first seconds of the film (over the Columbia Lady), the rousing adventure music comes on strong(with shots of oil wells hitting geysers) and then suddenly segues into that quiet little Anne Murray charmer of a love song(which will recur on a period record player to help nudge Scott and Dunaway into love.)
But the thunderous action score comes back again and again and keeps Oklahoma Crude more exciting than it maybe really is.