Broadway Maladies : ALL HIS JAZZ; The Life and Death of Bob Fosse <i> By Martin Gottfried (Bantam: $24.95; 460 pp.) </i> : INVENTING CHAMPAGNE; The Musical Worlds of Lerner and Loewe <i> By Gene Lees (St. Martin’s Press: $22.95; 352 pp.) </i>

It used to be called the longest street with the shortest memory. No longer. Today, just about all Broadway has is its souvenirs. The American musical, one of our few native art forms, is shuffling off to extinction. Of the seven home-grown productions currently on display, five are revivals of a time that will come no more.

And yet until quite recently, the Broadway melody was our unofficial anthem. You don’t have to go back to the palmy days of the Gershwins, Rogers and Hart, Jerome Kern or Cole Porter. After all, it was only three years ago that one of the theater’s most influential directors suffered a fatal heart attack on a Washington street. The 60-year-old had been rehearsing numbers half a block away.

Bob Fosse went out of show business the way he came in: full of an inexhaustible appetite for success and self-annihilation. This is no news to anyone who saw “All That Jazz,” Fosse’s autobiographical film that oscillated between hagiography and hatchet job. But as critic Martin Gottfried shows in this intelligent anecdotal study, the man was neither as imperial as he claimed nor as vile as he felt.

Fosse was brought up in a religious home on the North Side of Chicago. Pop sold insurance; Mom saw to it that the five kids got an education. Bob’s was in a dancing school, and then as part of an act called the Riff Bros. The innocent teen-ager hoofed and puffed his way into burlesque. “I was really unhappy and scared,” Fosse was to recall. “It left certain impressions on me that weren’t too good. I was too young to be exposed to naked ladies.”

Fosse never really outgrew that period. In his work, sex became tinged with guilt and voyeurism. In private life, the permanent adolescent, doubtful about his masculinity, kept trying to reassure himself with nonstop affairs. They persisted through three marriages--the most enduring to Gwen Verdon--and they continued beyond his early success as a $100-a-week choreographer of “Pajama Game,” past the time in 1972 when he won a Tony for “Pippin,” an Academy Award for “Cabaret” and an Emmy for a Liza Minnelli special. By then, he was living on Dexamil, and no sexual or professional triumph could last. After receiving the triple crown, he told friends that he felt “terrific for six days. Then, after seven, I thought, ‘It’s all false.’ They made me feel I fooled everybody.”

But as “All His Jazz” painfully records, if Fosse fooled anyone it was himself. From opening night to final curtain, he kept the con in confidence. His nervous energy provided the supercharge in all of his shows, but the theater and its audiences were changing before his myopic eyes.

Fosse’s last production flopped out of town. The musical he was rehearsing when he died was a revival of an old hit, “Sweet Charity.” It was an irony he might have relished: Broadway’s progressive force was looking in the rear-view mirror when he crashed. Fosse could have made a movie of it. But not a musical. These days, British imports entice the advance sales: “Phantom of the Opera,” “Cats,” “Aspects of Love,” “Les Miserables,” “Miss Saigon.”

Then again, the American theatergoer always has been an Anglophile, something that Alan Jay Lerner and Fritz Loewe emphatically demonstrated on March 15, 1956. That was the night “My Fair Lady” opened at the Mark Hellinger. Recalling the epochal moment, Gene Lees writes, “Lerner and Loewe, were now the royalty of the theater.” That is a fair summary of the collaborators’ professional status--and the prose style of “Inventing Champagne”: Lees, author of books about Oscar Peterson and a number of jazz singers, seems far more comfortable with the ambiance of smoky nightclubs than in the autumnal atmosphere of Schubert Alley.

Still, his subjects are so complex and contradictory that they might elude a gaggle of Pulitzer Prize authors. Loewe was the ur -Viennese composer whose forebears included Lehar and Romberg. Lerner was made in America, born to wealth, educated at Choate and Harvard, where he was a classmate of John F. Kennedy.

Loewe was married (and divorced) once, and had one main collaborator. Lerner was married eight times, and had eight creative partners. Loewe refused to get excited by adverse criticism or bad luck; disdain was his weapon. Lerner was born with sand under his skin; any slight, real or imagined, was enough to upset him for weeks. Out of these differences arose a creative tension that produced “Brigadoon” and the lesser “Love Life” before the team crested with “My Fair Lady.”

They were never to find that form again. The rich score of “Camelot” brought them renewed attention, but the production was in fact a slovenly and hazardous affair. In the end, nobody seemed to know what it was trying to say or be. Especially Lees.

“The story,” Lees informs us, “is about two men who love each other having an emotional and continuing physical relationship with the same woman, which after a time becomes obvious as a homosexual fantasy.” (This interpretation would come as a surprise to Lerner and Loewe, to say nothing of Thomas Malory, who started the whole thing by writing “La Mort d’Arthur” in the 15th Century.)

Director Moss Hart suffered a heart attack during the production of “Camelot.” So did Loewe. Lerner avoided the cardiologists. He had bleeding ulcers. “We will all be replaced tomorrow by hospital orderlies,” Loewe cracked. It was truer than he knew.

In better times, the elegance of “Gigi” burnished the reputation of the composer and lyricist, but today the movie has a slightly cobwebbed look, as if it had been written about another century in another century. Loewe eventually retired to his yacht, his gambling and his harem of young women. Asked whether he missed the creative process, the composer replied, “I have discovered the bedroom.”

Like Fosse, Lerner persisted in the craft that would destroy him. Addicted to amphetamines and recognition, he worked with a series of collaborators on shows as varied as “On A Clear Day You Can See Forever” with Burton Lane to the catastrophic “Dance a Little Closer” (dubbed “Close a Little Quicker”) with Charles Strouse.

Nothing came close to the adventures of Liza Dolittle, and one day Lerner awoke to find himself irrelevant. His bitter observation seems more valid now than at his death at 67 in 1986 (Loewe passed on two years later, as old as the century itself.) With certain rare exceptions, Lerner noted, “the music in the theater today bears no resemblance to the music that is popular on the outside.”

Unless things change dramatically--and melodically--that line should serve as an obituary for the American musical. Then, in death, it can finally recover its singularity: Throughout all history, no art form will ever have fallen so far so fast.