It is extremely rare that a film composer receives this kind of attention from leading concert composers, so Rosenman must have done things right.
Both John Adams and John Corigliano are fans of him, especially of East of Eden and Rebel Without a Cause with Adams favoring the latter and Corigliano the former. Rosenman himself considered East of Eden his best score.
Here is what John Adams wrote about Rosenman in liner notes in the East of Eden and Rebel Without a Cause recording he conducted:
Leonard Rosenman is an important transitional figure in the history of film music: a highly skilled composer whose best work evolved during a critical period between that of old school Europeans like Max Steiner and Dimitri Tiomkin and that of the later, more pop-oriented composers of the 60s, 70s and beyond. Rosenman was doubtless one of the most thoroughly schooled musicans ever to work in Hollywood. Before making an acquaintance of director Elia Kazan in New York in 1954, he studied composition and theory at the University of California, Berkeley with Roger Sessions, the most serious of all serious composers. He was thoroughly familiar with all the latest modern techniques in the works of Stravinsky, Bartók and Schoenberg. Most importantly, he possessed one thing Sessions lacked: the common touch, an ability to mirror the American vernacular experience in his music. This was an essential ability for anyone hoping to make a successful foray into commcercial film music.
East of Eden, Rosenman's first score was an ideal vehicle for his talents. The John Steinbeck story combines homespun simplicities of mid-century American social realism with the darker, more symbolic themes of filial disobedience and Oedipal search for his the lost mother. Set among the lush and irresistible beauty of the northern California coast, this 1955 film took the young James Dean into almost instant celebrity in the role of the tormented, misunderstood and unappreciated brother and son. The story, with its consciously Old Testament motifs acted by an ensemble of exceptionally gifted performers, including Julie Harris, Raymond Massey and Burl Ives, is one of the better examples of what a major Hollywood film could achieve.
Rosenman's score is, when required, appropriately evocative of a "simple" American past (the story takes place during World War I). He utilizes both the widely spaced harmonies and simple diatonic tunes made famous by Copland, but Rosenman's ideas are never whole-cloth borrowings. His music has its own originality. The famous "Main Theme" with its innocent, almost childlike 3/4 lilt is one of the most memorable melodies in all American cinema. The music matches the qualities of Steinbeck's prose with uncanny exactness, at one moment being simple and plainspoken to the point of rusticity, and then modulating abruptly to a suppressed brooding that is far more sophisticated and self-aware than any earlier example of music for the screen.
Written a year later, Rebel Without a Cause was musically even more successful, although the film, with its portrayal of misguided, troubled American youth, lacked the depth and richness of the Steinbeck story. While East of Eden was a period piece evoking for the American viewer an already lost idyllic past, Rebel Without a Cause was harshly contemporary and showed a strong influence of film noir in its treatment of the subject and characters. It may well be the film that created the whole "Fifties" stereotype, with its pompadour male hairstyles, car fetishes, and gangs of disaffected teenagers given to casual violence and unable to communicate with their uncomprehending elders. It is perhaps not insignificant that his film predates the premiere of West Side Story by two years.
For the film, which provided another starring role for James Dean and an early appearance by all-too-worldly Natalie Wood, Rosenman created a complex score that moves effortlessly between the urban big band jazz of Stan Kenton and the moody atmospheres of Bartók and Stravinsky. Bartók's Music for Strings, Percussion and Celesta, hardly known to the general public in 1955, makes a particularly evocative model in film's "planetarium" scene, during which the 50s' newfound preoccupation with outer space and extraterrestial events is eerily worked into the film's existential themes. The fractured rhythms and polytonalities of Stravinsky's Rite of Spring are felt in the scenes of violence and terror, although here, as elsewhere, Rosenman never loses his own original voice. Unlike many a lesser film composer, Rosenman managed to avoid resorting to hasty pastiche or overt borrowing. The two scores show what could actually be achieved when a skilled composer and a director sensitive to the powers of music were allowed to work together under conditions of artistic freedom, unimpeded by the crush of market forces - a rare moment in an industry in which art and money always maintain a difficult equipoise. - JOHN ADAMS
During Sunday's pre-concert talk, conductor John Adams – who recorded Rosenman's East of Eden and Rebel Without a Cause suites for Nonesuch in 1995 – described the composer as "one of the most important, skilled and knowledgeable of all film composers." "Adams took the microphone during the concert to extol Rosenman's virtues, calling him a "sophisticated composer" who helped to bring "psychological depth" to 1950s films like Rebel Without a Cause."
John Corigliano: "East of Eden with Leonard Rosenman's music, is a great film on every level. It's like a combination of Berg and Barber and it's beautiful, and it has a simple American melody also of pure innocence. That score is great. It's so powerful, and in addition to that highly chromatic and nervous, wonderful sinewy beauty he also has an innocence like Copland. It should have a symphonic version played by major orchestras".
My own favourites, aside from East of Eden being my absolute favourite Rosenman score - a score that reside within my top 25 film scores of all time, I think I even mentioned it among my top 10 the last time I did a top 10, include Rebel Without a Cause, Fantastic Voyage and A Man Called Horse - those are the four big Rosenman's favourites I have.
I might be alone, especially on this forum, but I prefer Rosenman at his best music over Williams at his best. Williams has more "good" scores to his name, but I still prefer Rosenman's best music over Williams's best music. I might also rank Rosenman above Williams on a top 10 film composers list.