Q: When is an opera not an opera? A: When it’s a Broadway show. Q: Then when is a Broadway show not a Broadway show? A: When it’s an opera. Q: So how do you tell the difference? A: That’s a tough question. These days, a very tough question. For too long “opera” has been narrowly + defined as what goes on at the Metropolitan Opera House; a rigid distinction between art and entertainment, fervently defended by a musical flat-earth society, has denied audiences the riches that lie beyond the narrow shoals of the classical repertoire. Today, though, singers and conductors are making the voyage and discovering a brave new world on the other side: America’s own authentic artistic heritage. Broadway, say hello to high class. Since 1985, when Leonard Bernstein’s 1957 musical West Side Story was released with an operatic cast that included soprano Kiri Te Kanawa and tenor Jose Carreras — and sold handsomely — other shows have got the tony treatment on records: Rodgers and Hammerstein’s Carousel and South Pacific , and Lerner and Loewe’s My Fair Lady . Now, most impressive of all, comes Jerome Kern and Oscar Hammerstein II’s 1927 musical adaptation of Edna Ferber’s novel Show Boat. With a cast that features opera stars Frederica von Stade , Teresa Stratas and Jerry Hadley , as well as a cameo appearance by Lillian Gish as the Lady on the Levee, this Show Boat aims high. “Show Boat was thought of as a dusty operetta, but it is really a moving piece of music drama,” says conductor John McGlinn, 35, whose passion for the score drove him to record the Mississippi riverboat musical in its complete 1927 version. McGlinn restored the overture, reinstating three important ensemble numbers and, most controversially, insisting on Hammerstein’s original dialogue, which includes use of the word nigger. The result is a Show Boat wiped clean of the sentimental and sanitized patina it had acquired over the years. In its place stands a raw, powerful and angry work whose seriousness of purpose and lofty artistic aspirations are umistakable. Not all the recordings have been as musically successful as Show Boat. In West Side Story, Carreras’ Hispanic accent was as wrong for the role of the New Yorker Tony as Te Kanawa’s British inflection was for the Latino Maria. In South Pacific, the casting of tenor Carreras, in the role created by bass Ezio Pinza, was a bit of commercialism that necessitated transposing the part and ended up distorting the balance. Further, imagining the New Zealand-born Te Kanawa as an all-American Nellie Forbush was a greater suspension of disbelief than many listeners were willing to make. Yet My Fair Lady was solid and assured, even if Jeremy Irons did not erase the memory of Rex Harrison as | Henry Higgins. And Carousel, with songstress Barbara Cook and opera bass Samuel Ramey as the ill-fated lovers, was thrilling.