By the time he was tapped to compose the film score for Clue, John Morris had enjoyed a long career writing music for TV and movies. He worked closely with Mel Brooks and scored lots of movies for him over the years including The Producers, Young Frankenstein, and Blazing Saddles.
Plus, in 1980, he was nominated for an Oscar for his score for The Elephant Man. The guy was good. Real good.
Like the movie, the score to Clue mixes two seemingly contradictory elements—comedy and murder.