FIFTY YEARS ago next Tuesday night the National Theater presented the first performance of a musical play that would change the course of the American musical theater. It was called "Show Boat," and its torrent of songs soon became part of our lives.

The score includes "Ol' Man River," "Bill," "Can't Help Lovin' Dat Man," "Only Make Believe," "Why Do I [WORD ILLEGIBLE] You?," "You Are Love," "Life Upon the Wicked Stage" including the black Jubilee Singers, today would be economically unlikely.

Its beginnings came during the tryout of a play novelist Edna Ferber adapted from one of the her favorite short stories, "Old Man Minick." To cheer the cast after a dismal tryout, producer Winthrop Ames remarked that for his next tryout, he'd rent a show boat and drift down the Connecticut River. "What's a show boat?" asked Ferber.After two years of investigation and writing, she would dedicate her novel "To Winthrop Ames Who First Said Show Boat to Me."

The book took off the summer of '26 as an early "Book-of-the-Month Club" selection. One first excited reader was Jerome Kern, who had composed over 20 Broadway hits during 15 lively years. Kern urged Oscar Hammerstein II, lyricist and librettist for his "Sunny," to read it. Oscar, grandson and son of major theatrical managers, was then working on "The Desert Song," with "Oklahoma!," "South Pacific" and his Richard Rodgers partnership far in the future.

Accounts differ, but Hugh Fordin's "Getting To Know Him: A Biography of House will publish next month, relates the next step with period humor. At the opening of Kern's "Criss Cross," composer Kern rushed up to critic Alexander Woollcott, who was talking with a woman in the theater lobby. Kern knew that Woollcott was a friend of Ferber's. Could Woollcott arrange for Kern to meet her? Fordin writes:

"Woollcott, with his usual relish for the dramatic, said musingly, 'Mmmm, well, it might just possible be arranged if you'll have patience and let me do things my own way. I think I can just do it if I play my cards right.' 'oh, thanks,' said Kern, 'Thanks awfully, Aleck. I'll be waiting.'

"Now Woollcott pounced on his dramatic moment. Turning to the woman beside him, he said, 'Ferber, this is Jerome Kern, Jerry, Edna Ferber."

Within days Hammerstein and Kern agreed on their aim and Floren Ziegfeld had become producer, paying Ferber $500 for a royalty advance. But the show would take longer to pull together than expected. Such things always do.

Next month, to celebrate the 50th anniversary of "Show Boats" New York opening (Dec. 27, 1927), the Oxford University Press will publish a lavishly illustrated jumbo-sized volume about the musical and its many versions the world has seen on stage and screen. Its author is fiercely determined historian of our musical theater and film, Miles Kreuger, president of the Institute of the American Musical. Oxford is hoping the binders finish their job in time for the Christmas sales. ("Show Boat: The Story of a Classic American Musical," 300 illustrations, $19.95)

Kreuger's advance galley pages reveal a wondrous labor of musical show passions. He has tracked down details, castings and, above all, precisely how Hammerstein's adaptation differs from version to version, including three films. He demolishes such legends as the one that "Show Boat" would open Ziegfeld's beautiful, now vanished, theater on 54th Street, and he explains why Paul Roberson missed the chance to create Kern's "Ol' Man River," which he'd first sung to Ferber.

(The anniversary also has sparked publication by Crown of another large-sized volume. "The Best Musicals from 'Show Boat' to 'A Chorus Line,'" a volume you'll wisely save $15.95 by not buying. Its caption lines are unpardonably scanty, faces unidentified, it's discography quixotic and when editor Arthur Jackson discusses "Show Boat" there's not one mention of Ferber.)

"Show Boat" rests on Ferber, Hammerstein and Kern. In her 1939 autobiography, "A Peculiar Treasure," Ferber tells of visiting one of the rare surviving barges (which is what they were, always towed, not puffing steam as in the glossy movies), the "James Adams Floating Theater" on lower Chesapeake Bay. Later Hammerstein would find the same (or possibly another) further up the Chesapeake, and while he loved its people, he hated their mechanical performance and slipped away, not surprising for the scion of the period's most discriminating managers.

Hammerstein's definition in shaping Ferber's sprawling story to the stage proved the musicals vital factor, though Act II always has been troublesome. He blended some of the characters, elided incidents and, above all, saw the setting about interracial marriage and a wife's desertion by her gambling husband, far from the usual '20s musical material. Hammerstein's creativity is best exemplified in his use of the Mississipi as an over shadowing presence.

Norma Terris, now living in Connecticut, was the first Magnolia. Her successor was Irene Dunne. Howard Marsh became Revenal on the defection of Harry Fender, who forsook the nervous world of Broadway to become a St. Louis policeman. Julie, of mixed blood, was played by Helen Morgan, who set a stage vogue by perching atop an upright piano for "Bill." The most familiar members of the first cast were Charles Winniger and Edna May Oliver, as Cap'n Andy and his wife, Parthy.

A noted husband-wife vaudeville team. Eva Puck and Sammy White, played the Cotton Blossom's husband-wife team. Jules Bledsoe, a black concert artist ranked just under Robeson, introduced "Ol' Man River" because Robeson had previous commitments. Tess Gardella, an Italian singer who worked in blackface as vaudeville's "Ant Jemima," created Queenie, who lead the "Can't Help Lovin' Dat Man" steps.

How is it that instead of a bang-up revival for this anniversary, we must settle for a book? As I is exemplary, but Act II troublesome for its staging and credibility. But Kreuger has a telling point: "Perhaps it is time to recreate 'Show Boat' in the form that inspired critic Robert Garland to call it on opening night simply: 'an American master piece.'"

The Kennedy Center should give it a proper revial, not the thin shadow it presented a few years back. Maybe the new Duke University Musical Theater will do it up right. In our 201st year, it's time we had a production worthy of "Show Boat." If "A Chorul Line" can sell out the Opera House for six weeks, Kern's score could do it for 12 Betcha.