You could make a case that Kern and Hammerstein's theatrical adaptation of Show Boat has been given too much credit for its influence on the form of the American musical and not enough credit for its contribution to the American dialogue about race.
If you think about it, the so-called “integrated book musical”, with songs that arose naturally out of the story and served to advance the drama and delineate character, already existed on the world's stages in the form of operettas. Operettas in the early 20th Century were often semi-serious, romantic dramas — not all that different from Show Boat — and by the time Hammerstein wrote the book and lyrics for Show Boat he had already written the books and lyrics for several operettas. Kern had gotten his start in theater supplying additional songs for Continental operettas in their British and American incarnations.
The radical innovations of Show Boat were not so much formal as tonal and stylistic. It eschewed the European atmosphere of traditional operettas and their farce-like plots, often involving a romance between two people who belong (or more commonly think they belong) to different classes. And it added to the operatic style of music evoked in operettas distinctly American strains, derived from an African-American musical tradition.
More than this, it created a kind of dialogue between the European operatic tradition and the African-American musical tradition — a dialogue which is incorporated into the interactions between black and white characters in the story itself. The African-American music used in the play is pre-ragtime, pre-jazz, although those innovations are alluded to in the play's concluding scenes. Mostly, however, Kern's score deals with spirituals and the kind of lightly syncopated music associated with the minstrel stage — the cakewalk and the shuffle.
The African strain, of course, is what makes American music American. It's the American quality of the Show Boat score that makes it so distinctive, so unlike anything which had gone before — and it's the explicit recognition and dramatization of the African cultural influence that makes Show Boat such a resonant meditation on American culture.
When the curtain opened at he premiere of the show in 1927, the first word that came from the stage was “Niggers”. It came from the mouths of black laborers loading cargo onto boats at the dock where the Cotton Blossom Floating Palace Theater was tied up. “Niggers all work on the Mississippi,” they sang. “Niggers all work while the white folks play.” That first-night audience saw the white folks' playhouse, the show boat, where blacks couldn't play — a fact soon to be made explicit in the text when a member of the Cotton Blossom troupe (Julie LaVerne, played by Helen Morgan, above, in the stage production and in the 1936 film) is exposed as a woman of mixed race and expelled from the show boat community. All the while, the music of black America pervades the playhouse, shapes the entertainment offered there.
This was bold stuff in 1927, and when Show Boat became a beloved American classic, even Hammerstein retreated from it. In subsequent revivals, the word “nigger” was done away with. The first line of “Ole Man River” was changed to “Darkies all work on the Mississippi” and then to “Colored folks work on the Mississippi” and then to “Here we all work on the Mississippi”.
Something of the deep and transgressive irony of Hammerstein's original inspiration was lost in the process — just as something of Twain's deep and transgressive irony in Huckleberry Finn would be lost if the word “nigger” were to be removed from that book. Certainly removing it from Show Boat makes us feel better — but it was there precisely to make us feel uneasy.
The troublesome themes of Show Boat remain, however, even when its language is prettied up — and its themes, far more than its supposed formal innovations, are what make it perennially radical and important.