The Musical Theatre: A CELEBRATION <i> by Alan Jay Lerner (McGraw-Hill: $24.95; 280 pp., illustrated)</i>

For Americans, to call someone a vulgarizer sounds dreadful; it conjures up visions of somebody slurping from finger bowls at fashionable dinner parties. But for the French, to call someone a vulgarizer is an honorable thing, for it simply means someone who popularizes a serious subject. His work may not provide comprehensive scrutiny and analysis, but that is not his aim, or the expectation of his readers, who want a large, complex subject explained in laymen’s terms. The trick is to do it with an intelligent structure, uncommon insight and elegance of style.

“The Musical Theatre,” by Alan Jay Lerner, is a popular history of musical theater from the creation of operetta by Jacques Offenbach to the present day. Lerner, who died last July, was well qualified to write such a book. Not only was he a world-famous librettist and lyricist (or lyrist, which he reminds us is the correct term) through his authorship of such works as “Brigadoon,” “My Fair Lady,” “Gigi” and “Camelot,” but he was also very well schooled in the history and mechanics of his disciplines. Furthermore, he lived through what he refers to as the “Belle Epoque” of musical comedy as a vital contributor who knew its major figures intimately. In all ways, he was there.

The book is essentially a chronological survey for the reader who wants an overall understanding of the background of musical theater. Lerner defined terms, identifies and follows trends and movements, and, especially, illustrates the changing form of musicals by analyzing the careers of the men and women who wrote them. He is witty and succinct, infusing all with the delight he obviously took in his profession. The book is subtitled “a celebration”; his effulgent style makes one clearly see why.

There are several reasons why this book makes a fine introduction to musical theater. One is that Lerner knows exactly what was new, and when and why. He pinpoints the true beginning of operetta as an art form to Offenbach’s “Orpheus in the Underworld” in 1859, then follows his influence through Gilbert and Sullivan (“The Pirates of Penzance” was based on “The Brigands”) to Franz Lehar and his ilk, whose fluffy, romantic operettas were direct descendants of “La Perichole.” He notes the worldwide influence of “Alexander’s Ragtime Band,” which changed the entire world, the theater included, by making it unavoidably aware of jazz in 1911. He points out that “They Didn’t Believe Me,” with its built-in, unobtrusive afterbeat (which defines jazz) began the modern musical theater in Jerome Kern’s “The Girl From Utah” in 1914. It’s all very clear and precise.

Second, he knows a hawk from a handsaw, and so can surprise us with the observation that the most popular “Viennese” waltz ever written, the “Merry Widow” waltz, is actually not a Viennese (hesitation) waltz, but a French waltz (on the beat). And what a delight it is to be shown that Vincent Youmans’ “Tea for Two” is a unique melodic invention, a dotted quarter-eighth-note song from beginning to end, whose “dummy,” or practice, lyric was judged to be perfect and became world famous, much to lyricist Irving Caesar’s horror.

Third, he distills the essence of each major figure’s contribution; and this he does with great affection, whether it’s telling us the names of the men who made up the world’s first jazz combo, the Razzy Dazzy Spasm Band, or gracefully paying tribute to the career of Otto Harbach, one of the finest, most influential lyric writers of the 20th Century, and the most underappreciated. He brings an informed appreciation to the accomplishments of careers from Siegmund Romberg and Rudolf Friml to Stephen Sondheim and Andrew Lloyd Webber, stopping along the way to tell of the dissolution of the lives of Lorenz Hart and Vincent Youmans with great compassion, or castigate Nazi sympathizer Lehar with the memorable line, “to this day, when I am transported by the music of Lehar, my glass of champagne is rimmed with aloes.” He knows who these people were as well as he knows the value of what they did.

Journalism is notation of the passing scene, but history is perspective on it. Though you come away from “The Musical Theatre” with a good sense of what fit where and why it was important, there are times you wish Lerner wouldn’t gush so. Is it really true that “there is little doubt” that George Gershwin “was the greatest musical genius that America has produced”? That opinion does not seem to have penetrated to the hallowed halls of such places as Juilliard and the Manhattan School of Music. Is George Kaufman’s line, “you can lead a horticulture but you can’t make her think” truly “the most brilliant pun of the 20th Century?” Does it put puns like James Joyce’s “lawn Tennyson” in the shade? And how do you judge the most brilliant pun? Isn’t that a bit like citing the world’s most perfect diamond chip?

On the other hand, to call “Ol’ Man River” “the profoundest lyric ever to emerge on the musical stage,” and the title song of “Lost in the Stars” “as touching and heartbreaking a blend of music and lyrics as I know” seem perfectly apt. When he says that “musical theater is fundamentally a popular theater and a spontaneous expression of its time,” and therefore he believes that there is no such thing as an avant-garde musical, he is provocative. When he writes of Irving Berlin, “his songs have a musicianship equal to those of the most trained composer. His lyrics touch the center of every emotion, always pure, always simple, always direct, but never banal. What he wrote said it for everyone,” Lerner is sublime.

And what a relief it is to find one breast that is not overheated when the subject of Sondheim comes up. He acknowledges the brilliance, polish and originality of his remarkable work, but also its joylessness and lack of melodic flights. His consistent lack of popularity with the public does not get by, nor does the arrogance of referring to the work of Hart as “mostly technically sloppy, unfelt and silly.” He skewers Sondheim’s goal in “Pacific Overtures” “to tell a story that has no characters at all,” by observing that “a plot without living people can only be found in a cemetery.” He would have agreed with Victor Samrock, the dean of Broadway managers, who recently said: “Sondheim is unquestionably the best of his kind and in his time.” In “The Musical Theatre,” one is privy to the judgment of a man who knows how that comment applies to the most significant figures throughout the history of the musical, and who expresses his opinions in a forthright, warm and personal manner.