Leonard Bernstein (1918 - 1980) was an American composer who wrote in many different styles but his best known work was West Side Story. I once saw him in a documentary trying to get the Spanish classical singer José Carreras to sing in a jazz rhythm. There is a clip from the film here.
Classical vocalists seem to have a problem with off beat rhythm's and Bernstein, who often wrote jazzy tunes, lost his patience.
I have chosen his Candide Overture as my favourite Bernstein melody and the track below is of the Bournemouth Symphony conducted by Andrew Little.
Leonard Bernstein discography can be found here.