From Longman Dictionary of Contemporary Englishmonotonemon‧o‧tone /ˈmɒnətəʊn $ ˈmɑːnətoʊn/ noun [singular] CBORINGa sound or way of speaking or singing that continues on the same note without getting any louder or softer, and therefore sounds very boring He answered all the lawyer’s questions in a dull monotone.
Examples from the Corpus
monotone• Jim Feng laughed quietly: a monotone chuckling.• In a barely audible monotone, she gave her evidence.• For the past two hours they had listened to Wingate answering questions in a flat exhausted monotone.• His message is one of Reaganesque optimism, incongruously delivered in a Forbesian monotone.• Instead, I wanted to be Choo Choo, who wore a long turtleneck and spoke with a high monotone.• It is monotone, mechanical and Daleky.• Duvall drawled in a strange monotone.• An engaging blend of poetic characterization and deductive reasoning, it was delivered for the most part in a weary monotone. 