The small, two-story building at 636 Christian St. is only a 15-minute stroll from the corner of Broad and Market streets, the intersection that is sometimes considered the very center of Center City Philadelphia. But to take that walk is to venture into a different land--into a miraculously preserved ethnic enclave in the midst of what has become a vast international city.

From the vantage point of Christian Street, the skyscrapers of central Philadelphia loom like glittering steel sentries, as distant and unreal as the Emerald City must have seemed to Dorothy from her poppy field. South Philadelphia is a world unto itself--where the houses are modestly scaled yet meticulously maintained, where Ralph's Restaurant still serves the heaping, flavorful plates of spaghetti pomodoro that have been its specialty for nearly a century, where neighbors hail one another from across the street (and regard outsiders with polite but decided reticence), where the accent is overwhelmingly Italian.

It was in an upstairs bedroom at 636 Christian St. that Alfredo Arnold Cocozza bellowed his first on Jan. 31, 1921. If you are lucky--or merely tenacious enough in your inquiries--you may still find somebody in South Philly who knew the Cocozza family, who may have shopped in the tiny grocery the Cocozzas operated below their cramped apartment, who joined in the neighborhood celebrations on those uproarious occasions when young Alfredo returned home in triumph, after he had become world-famous as Mario Lanza.

Four decades after Lanza's death, the tenor's name (adopted from his mother's side of the family) is still celebrated--and not just in Philadelphia. There have been half a dozen biographies by now, the most recent (and most authoritative) by Roland L. Bessette published earlier this year by Amadeus Press. Lanza's recordings continue to generate more than $100,000 every year for his estate, a staggering sum for a classical or semiclassical musician who has been gone so long. And Lanza's films--particularly the ones he made for MGM, such as "That Midnight Kiss," "The Toast of New Orleans" and "The Great Caruso"--are still staples on late-night television and can sometimes be found in video stores.

Tenor and Washington Opera Artistic Director Placido Domingo has acknowledged that "The Great Caruso," in particular, exerted a great influence on his career. So has Luciano Pavarotti, who, according to biographer Bessette, "pinpointed his early aspirations to a sense of awe at hearing 'Be My Love,' " Lanza's greatest hit, as a teenager in Italy. "Third Tenor" Jose Carreras has gone even further: Lanza's "wonderful voice and the charismatic appeal of his personality had a profound effect on my life, and I decided there and then that I too would one day sing the great operatic roles." And last summer in Chicago's Grant Park, some 12,000 people showed up to hear tenor Richard Leech narrate and sing a tribute to Mario Lanza.

Obviously, a lot of people are still out there listening. Yet Lanza is rarely taken seriously by classical music aficionados. You will search in vain for his name in most of the critical histories of recorded opera, despite the fact that he recorded many of the best-known arias in the repertory. He is often dismissed as a vulgar bawler--or, at best, as a calculated creation of big money and bigger hype, like Andrea Bocelli.

Still, conductor Arturo Toscanini is said to have called Lanza's "the greatest natural voice of the 20th century." The attribution is a little shaky--it was first published two years after the maestro's death--but there can be no doubt that other unquestionably important musicians held Lanza's gift in awe, among them the conductors Serge Koussevitzky and Julius Rudel, the baritone (and onetime artistic director of the Kennedy Center) George London and the soprano Licia Albanese, who recorded with Toscanini as well as such legendary tenors as Beniamino Gigli and who once said that Lanza had "a greater voice than Caruso."

Lanza himself had no doubts that Albanese's assessment was correct. "Caruso?" he once said. "You study that ridiculous legend? That guy could not even whistle properly."

This last quote may provide a clue to the reason Lanza's star imploded at just the moment it should have been forever established in the firmament. For there is no getting around the fact--despite his abundant talent, Lanza could be a lazy, strutting, arrogant and undisciplined jerk. He had an insatiable appetite for food, liquor and women, all of which he abused with shocking insensibility. He could barely read music, and refused to learn, preferring to mimic the recorded performances of other people. He was known to balloon up to 250 pounds in the middle of making a motion picture, sometimes delaying production by months. Even Bessette, in what is generally a warm and sympathetic biography, acknowledges that Lanza is "a strong contender for the title of the most truculent, morose, demanding star in the history of Hollywood."

He had the endearing habit of urinating whenever and wherever he felt like it--sometimes in front of his leading ladies and, on one memorable occasion, out the window of Philadelphia's tony Bellevue Stratford Hotel in full view of some astonished reporters. He was a foul-mouthed and belligerent colleague who regularly addressed women in the vilest of terms. Despite the fact that he was one of the top-grossing stars at MGM, he was summarily fired by studio boss Dore Schary.

Later, when he was hundreds of thousands of dollars in debt, Lanza drank his way through an extended Las Vegas engagement that might have quickly restored his solvency but resulted instead in a devastating lawsuit. On Oct. 7, 1959, at the age of 38, he died in Rome from what was diagnosed as a heart attack. As with the case of the extraordinary jazz musician Bix Beiderbecke, it might be better said that Lanza really died from "too much of everything."

It is naive and idealistic to expect our great artists to be great human beings as well. Some are, some aren't; the actress who transcends all of our pretenses and frailties, touching our soul with her art, may be frostier than February when she is offstage, and the wittiest and most companionable of storytellers are often revealed to have been dour, disdainful and bitter men. It doesn't matter: In the long run, the shortcomings of Mario Lanza the person will be forgotten. But what of Mario Lanza the artist, as immortalized in his films and recordings?

Such early films as "That Midnight Kiss" (1949) and "The Toast of New Orleans" (1950) present us with a spirited, affable and charismatic young man who seems born to sing. These are light romantic comedies, ingratiating rather than laugh-out-loud funny, both of them based loosely on Lanza's own life--the poor but plucky boy with a terrific voice who rises to the top of society and gets the girl. Fifty years later, we can still understand Lanza's immediate appeal. The postwar era was one of rapid and profound democratization, and Lanza seemed a "normal guy" (albeit an unusually handsome and gifted one) with none of the supposed "elitism" Joe Sixpack generally associated with the world of opera.

"The Great Caruso" (1951) was more problematic--and not merely because this cinematic biography had virtually nothing to do with the facts of the Neapolitan tenor's life. Here Lanza was actually setting himself against Caruso, in some of the most celebrated arias in the repertoire, and here the young man's shortcomings began to show.

For Lanza had never received either the training or the seasoning that might have placed him among the important opera singers. He was offered the training--he worked with a number of vocal instructors throughout his career, most of whom ultimately threw up their hands at his lack of discipline and unwillingness to practice. But he had no time to grow; he appeared only a few times in operatic roles, for the simple reason that he became a star so quickly, through his concerts and radio appearances. After Hollywood had enfolded him, he elected to lose himself in the ready-made Satyricon available to handsome celebrities rather than in the service of a noble art.

And so what we hear, again and again, throughout Lanza's films and recordings, is magnificent and tragically unfulfilled promise. The voice was an extraordinary one--immediately distinctive in its sound throughout all registers, full of sun and ardor, lyrical yet immensely powerful, all combined with what (onstage, at least) was an exuberant and winning personality. Lanza always seemed to sing directly from the heart, from one person directly to another, and this is something that has eluded many better-trained artists.

But he often displayed a tendency to sob and shout--as if to overwhelm the listener even when nothing of the sort was called for. Somebody once said that Caruso always sang as if he were about to burst a vessel; the same can be said, with much greater acuity, for Lanza. He brought a desperate urgency to such masterpieces of bel canto as Donizetti's "Una furtiva lagrima," which ought to spin out naturally, as if an inward reverie.

Moreover, Lanza's phrasing, for all of its occasional charm, was too often sloppy and unreflected. The very spontaneity that was one of his principal gifts also worked against him; we too often have the sense that he is merely singing the way he feels at the time, rather than making a conscious decision about the course he wants to pursue in the delivery of a song or aria. (Indeed, there are times when it is difficult to believe he knew what the words he was singing really meant.) Here, Lanza could have taken lessons not only from professional opera singers but from his contemporary Frank Sinatra, the brainiest of all pop phrasers.

The soprano Frances Yeend, who worked closely with Lanza throughout his early career, once said that the tenor "provided a great treat for the ear, but nothing for the mind." This is not quite fair, for there can be little doubt that Lanza still "owns" such popular hits as "Be My Love," with that explosion into a luscious and unforgettable radiance on the word "love." Moreover, he brings an enormous and idiomatic charm to songs like "I'll Never Love You," "The Loveliest Night of the Year" and "Ciribiribin." Even if one believes, with Yeend, that the tenor provides "nothing for the mind" in these songs, certainly he provides something for the heart.

There is no way to assess Lanza's career as anything but a tragedy. He was yet one more victim of the ferocious struggle between talent and self-destruction that has so often plagued American music, from Stephen Foster through Jimi Hendrix and beyond. If his artistry had kept pace with the sheer abundance of his gifts, Mario Lanza might now be remembered as America's leading tenor. But it was not to be.

Still, out of the chaos and disrepair of his life, Lanza left us a number of recordings and motion pictures that are still listened to with appreciation and affection throughout the world. All things considered, that's not a bad legacy.

Mario Lanza on Disc

"The Mario Lanza Collection" (RCA Victor) is a three-disc release that covers most of the familiar material--from the hits through excerpts from opera and operetta through novelty numbers such as "Boom Biddy Boom Boom." For those who want more than three hours of Lanza, this is the place to start; for those who want merely a taste, there is a "Lanza's Greatest Hits" album available too.

"Don't Forget Me" (RCA Victor) is taken from Lanza's recordings for the Coca-Cola radio broadcasts between July 1951 and May 1952. The voice was still fresh and full, and Lanza often brought an agreeable informality to these sessions.

"Mario Lanza Live From London" (RCA Victor). The first thing that will shock anybody listening to this late concert performance (recorded in London's Royal Albert Hall on Jan. 16, 1958) is just how dark Lanza's voice became toward the end of his life. Some of his power is gone and the high notes are no longer so fresh as they once were. But one senses what could have been a deepening artistry in selections such as the "Lamento di Federico" and "A Vuchella."

Lanza on Videotape

"That Midnight Kiss" (1949) is still a charming film. Lanza was teamed with soprano Kathryn Grayson for this faintly autobiographical story of a young tenor; the superb supporting cast included pianist and conductor Jose Iturbi, Keenan Wynn and the 70-year-old grand dame of the American theater, Ethel Barrymore. (Typically, Lanza thought Barrymore was trying to steal his scenes and referred to her as an "old bitch.")

"The Great Caruso" (1951) is cited as a profound early influence by each of the fabled "Three Tenors." It has virtually nothing to do with Caruso's life--no, he didn't die onstage (although the baritone Leonard Warren did, at the height of his career). I find Lanza's way with the operatic repertoire in "The Great Caruso" decidedly ham-fisted, but the voice itself was still fine and strong.

"Serenade" (1956) is not a strong film, but it contains some of Lanza's best singing--including a remarkably credible performance of a 14-minute excerpt from that notorious and magnificent voice-wrecker, Verdi's "Otello," in which the tenor has Licia Albanese for a partner.

CAPTION: MARIO LANZA

CAPTION: Dorothy Kirsten and Mario Lanza in the 1951 film "The Great Caruso." Despite his abundant talent, the tenor could an arrogant and undisciplined jerk.