Often worked with director
Peter Glenville on both stage and screen; he
was all set to work with him again on the film version of "Man of La
Mancha" in 1972, but Glenville was dismissed after United Artists
learned he planned to eliminate most of the songs from the musical film
(he was replaced by
Arthur Hiller, who retained all but two of the
songs). Rosenthal stayed with the project and it is Rosenthal's orchestrations that are heard in the film; he also conducts the orchestra.