Which major key has one flat in the key signature?

Brought a new sophisticated and european influence to jazz piano and is today considered one of the most influential pianists of modern jazz. some of his more famous recordings are, sunday at the village vanguad and waltz for debby. he drew influences from the french impressionist composers claude debussy and maurice ravel, as well as bebop pianist bud powell. his playing can be described as lyrical, sensitive, and introspective yet with an underlining commitment to swing.