The following is from Chapter one of Sondheim’s Broadway Musicals by Stephen Banfield, page 37:
The presence of these songs in West Side Story reminds us what an extraordinarily wide range the music embraces. The verse of the “Balcony Scene” could almost be by Gounod, and the number is as old-fashioned and operettalike as the span and vocal stance of the “A Boy Like That” scena are grandly operatic. The “Cool” twelve-note fugue seems as indebted to Beethoven’s Grosse Fuge as does “Somewhere“‘s melodic contour to his “Emperor” Concerto and its sparse counterpoint to his late quartets, but at the same time the fugue’s and the “Prologue“‘s assimilation of modern jazz is astonishing and seems to anticipate third stream. The opening of the “Tonight” quintet is pure Stranvinsky, highly reminiscent of “Laudate dominum” in the Symphony of Psalms. The sheer verve and (especially in “Something’s Coming”) complexity of Bernstein’s Latin American rhythms can be as breathtaking as his film-music sentimentality in “Maria.” Everywhere his eclecticism risks all, as he treads what he sees as “the fine line between opera and Broadway” in “my baby, my tragic musical-comedy, whatever that is” (Peyser 1987, 236, 242).
The mixture of genres in the show as a whole is equally striking. Dance had never played such a vital role in a musical; this and the urban setting with its groups of characters ever on the move gave Bernstein scope for what was generically both a modern ballet score and a film score as well as a stage musical, and his experience with his previous “urban” scores, On the Town, Fancy Free, and On the Waterfront, led naturally into his fusing the three genres symphonically. The book, too, pithy as it is, had a crucial role to play: melodramatic scenes such as the bedroom interrogation and the drugstore episode with its chillingly inarticulate verismo dialogue at the end hold the stage as nonmusical drama through the exploitation of gangster film traditions and the like…the generic conventions of ballet, film, stage play, musical comedy, and opera intercut while remaining separate. That is why Maria’s final speech works perfectly well as dialogue despite being intended as a dummy lyric for music, and perhaps why the show has so triumphantly survived the embarrassments and weaknesses that time has forced upon its individual generic components.
This extremely valuable work discusses Sondheim's early training and subsequent career, his general compositional concerns, and his style. The meat of the book is a musical-dramatic analysis of his musicals . . . . For each musical, Banfield places the work and its components in a historical and typological text. He also treats in welcome detail the musical profile or universe of each show: Sondheim's use of generative intervals or interval complexes as source material, motifs that reappear in various guises in various songs, the sound world that defines the musical's emotional mind. The book will be as useful to those who are cool to Sondheim's work as to his fans --Choice