Maria Callas is dead at the age of 53. The world-famous opera star died unexpectedly in her Paris apartment yesterday of a heart attack.

Born on Dec. 3, 1923, in New York City's Fifth Avenue Hospital, and given the name of Cecilia Sophia Anna Maria Kalogeropoulou, Maria Callas became one of the greatest singers of this or any century. The child of poor Greek parents, she grew into an artist of unparalleled dramatic and vocal power, and a woman who rose from obscure poverty to great wealth. Unwanted by her mother, who refused to look at her new baby daughter for four days after she was born, Callas became a household name, and an intimate friend of some of the great and the rich of the past two decades.

Before her 27th birthday, Callas had signed a contract with one of the world's most prestigious record companies, and her name began to make its way around the world to become familiar to thousands of fans in countries where she had not yet appeared in person.

In 1950, she met Walter Legge, the husband of soprano Elizabeth Schwarzkopf and the founder of the Philharmonic Orchestra of London. He also was artistic director of EMI, the British industrial conglomerate that produced records known in this country under the Angel label. Legge, who had heard Callas' first recording made for the rising Italian Cetra company, had no doubts about the future of the Greek-American soprano. She was approaching her finest vocal years, and, primarily under the affectionately intense artistic scrutiny of conductor Tullio Serafin, she was becoming an artist of rare perceptions.

Dropping the heavy Wagner roles in which she had made an amazing beginning, Callas concentrated on the operas of Bellini, Donizetti and Rossini, with frequent visits in Verdi and Puccini territory. These operas are frequently and successfully presented today with Joan Sutherland, Beverly Sills, and Marilyn Horne taking on the razzle-dazzle vocal fireworks. It was Callas who first brought them to life through a coloratura technique that matched phenomenal agility with singular control of the essential element of pathos most of these roles demand.

The world's great opera houses opened their doors to Callas when they could get her. She sang at Milan's La Scala, London's Covent Garden, and New York's Metropolitan. Chicago's Lyric Opera heard her before the Met did, for she sang in Chicago in the fall seasons of 1954 and 1955, while her Met debut did not occur until October, 1956.

Her American operatic career never approached the numbers of performances she gave in Europe. She sang only 13 performances in Chicago, 21 at the Metropolitan. The last of these was a performance of "Tosca" in New York in March, 1965, when her partner was tenor Richard Tucker, with whom she had sung in Verona 18 years earlier.

After only two more performances in that same year, Callas called a final halt to her operatic career. But in 1973-1974, she sang in an extended concert tour with her longtime colleague, tenor Giuseppe di Stefano. That tour brougth Callas to Washington in February, 1974, for her only appearance in Constitution Hall.

Maria Callas was only 42 when she stopped singing in opera. Relatively speaking, that is very young for a singer to give up an operatic career. But the concrete reasons for her calling it quits may have had their roots in the first days of her life as well as in the startling changes in her way of living she suddenly arose at the height of ther powers.

In 1959, when Maria Callas was 36, she met Greek shipping tycoon Aristotle Onassis. She and her husband, Giovanni Battista Meneghini, had been invited for a summer cruise on the palatial Onassis yacht. The glamorous guest list that summer included, among others, Sir Winston and Lady Churchill. Somehow, the opera star who had become accustomed to owning magnificent jewels and all the other luxuries that go with great wealth, saw a new world. Was it colored by burning memory of a childhood of being unwanted, poor, and fat?

For whatever reasons, Callas had, as one of her favorite stage directors, Franco Zeffirelli, later said, "this stupid idea of becoming a great lady of cafe society." Though she had always been one of the most singularly dedicated of artists, Callas was draw is to a world in which leisure and yachts and Greek islands and freedom from the pressures of a career seemed infinitely desirable. They also seemed easily attainable.

Maria Callas hoped to marry Onassis.With this in mind, she renounced her U.S. citizenship - though tax problems also has their part in this move - and she had her marriage to Italian idustrialist Meneghini nullified. Since it had never been recognized by the Greek Orthodox Church, in which she had been christened, this was not difficult. When the Italian laws were later changed, she got a divorce.

Before that summer cruise was over, a triangle - Callas-Onassis-Meneghini - had come into existence. Callas has said of the end of her marriage, "The world has condemned me for leaving my husband, but I didn't leave him - he left me because I would not let him take care of my business affairs anymore. Battista himself said it was pointless if he had not complete power over me - that's all he wanted . . . I was kept in a cage so long that when I met Aristo and his friends, so full of life and glamour, I became a different woman."

Zeffirelli's comment on this was, "The whole Onassis episode took her mind away from the theater, shortened her career." John Ardoin, the finest of Callas biographers, wrote, prophetically, "Though Onassis was entranced by the woman and impressed by her celebrity, Callas the artist and musician meant little to him."

Walter Legge put it most succinctly of all when he said in conversation, "Maria has to make up her mind whether she wants to be the greatest singer in the world, or the mistress of a Greek shipping magnate. She cannot be both."

The Onassis affair reached right up to the point of marriage. Callas told "Ari" that it soon would be too late for her to have children, a long-cherished dream she did not intend to sacrifice. Onassis immediately agreed to a marriage, which was set for the first week in March, 1963, in London. Everything was arranged, and a Greek Orthodox priest was in flight from Athens to perform the ceremony when the couple had a ferocious quarrel that permanently broke up any prospect of a wedding.

Whether or not the growing friendship of Onassis and Jacqueline Kennedy was a major factor in the end of the Callas-Onassis affair is a matter of speculation. But within eight months of the break-up, President Kennedy's widow married Onassis.

The turbulence in Callas' personal life often was reflected in the more or less violent upheavals that marked her professional career. Again the reasons may have their origins in those faraways days of deprivation. Callas's close friends insist that underneath her secure and sometimes powerful exterior were all kinds of feelings of insecurity and inferiority.

Colleagues with whom she worked closely, both singers and conductors, however, are practically unanimous in declaring that Callas was unusual in her devotion to artistic detail and in her generous and helpful attitude toward younger singers.

Her unquestionably fiery temper led to public statements by Callas that the press, labeling her a "tigress" who was "violently temperamental," always built up into huge crises.

In 1958, Rudolf Bing, then general manager of the Metropolitan Opera, fired Callas when she declined to sing Lady Macbeth in Verdi's opera too close on the heels of a performance of Verdi's "Traviata." Citing the wide difference in vocal styles required for the two roles, Callas asked for some adjustment, which Bing peremptorily refused.

It took seven years for that rift to heal, but when it did. Callas said she felt that Bing respected her honesty and probably truled loved her. Bing said yesterday, that he was proud to have been in charge of the Met when Callas sang there.

In 1971, Callas showed a new side of her genius in a series of master classes she gave at New York City's Juilliard School of Music. The hundreds who crowded in to hear her working with gifted young singers fully expected her to know - as she did - everything about the soprano repertoire. But many of them admitted to real astonishment at the perceptions with which she coached baritones and tenors knowing every word and note of their scenes and giving them ideas and insights that no one else had thought of.

Maria Callas made an inconspicuous debut at the Olympia Theater in Athens in November, 1938, only a few days before she marked her 15th birthday. She sang the role of Snatuzza in Mascagni's "Cavalleria Rusticanna." The Callas family - the father, Georges, had made the simplified name official at the time Maria was christened in Manhattan's Greek Orthodox Cathedral - had returned to Greece in 1937, in the hope out financially with the young singer's musical training.

When Maria was still 14, her mother, who had decided that her unwanted daughter had a real talent for singing, took her to the Athens Conservatory where, by giving her age as 16, the future star was given free tuition for study with Elvira de Hidalgo, a coloratura soprano at the Metropolitan Opera.

De Hidalgo has described the Maria she saw at that time: "The very idea of that girl wanting to be a singer was laughable! She was tall, very fat, and wore heavy glasses. When she removed them, she would look at you with huge but vague, almost unseeing eyes. Her whole being was awkward and her dress was too large, buttoned in front and quite formless. Not knowing what to do with her hands, she sat there quietly biting her nails while waiting her turn to sing."

But when de Hidalgo heard the 14-year-old attacking Rezia'a aria, "Ocean, thou mightly monster," from Weber's "Oberon," she said she shut her eyes and began to imagine the pleasure of working with such material, "violent cascades of sound, not yet fully controlled but full of drama and emotion."

Greece suffered a difficult, rough time during World War II, first under German, then Italian occupying forces. Callas later remembered "real privation. We were poor and miserable: we lacked clothing and food which became more scarce daily. It was then that I suffered."

With the end of the war, Callas' years of daily study and work with de Hidalgo came to an end, though she kept in touch with her teacher and worked with her in the 1960s when she began to have serious vocal problems.

Her real professional debut occurred on Aug. 3, 1947, in the Arena in Verona, where she sang the title role in "La Gioconda," together with a young American tenor named Richard Tucker. It was at that time that she met two men who were to have great and lasting influences on her life and art.

They were the celebrated operatic conductor Tullio Serafin, and the Italian business magnate Giovanni Batista Meneghini, who became, in turn, the close friend, artistic patron, and finally, in 1949, the husband of Callas.

It was Serafin who asked Callas, not long after her first "Gioconda," if she knew the role of Isolde in Wagner's "Tristan." Callas, for fear that she might lose a chance if she said no said yes, of course she did. Whereupon Serafin produced the score and asked her to sing some of the second act while he played the piano.

Callas, a capable pianist and a fast and thoroughly dependable musician, sigh-read the part. Only afterward did she confess her deception to the conductor. Impressed by what he had heard. Serafin engaged her to sing the role the following December. Within little over a year, Callas proceeded to sing Isolde, "Turandot," "Aida," "Norma," Leonora in Verdi's "Forza del Destino," and Brunnhilde in Wagner's "Die Walkuere."

Only 10 days after her first Brunnhilde, Callas proceeded to sing one of the most demanding of all high coloratura roles, that of Elvira in "I Puritani." Not in 40 years since the days of Lilli Lehmann and Lillian Nordica, had any soprano mixed and matched the heaviest Wagnerian roles with the most dazzling of the bel canto coloratura parts. Within weeks, she had added to these the equally different and taxing roles of Kundry in Wagner's "Parsifal," and Abigaille in Verdi's "Nabucco."

The arguments over Callas's singing, her voice and her use of it, will not end with her death. But the evidence of her greatness is present in hundreds of recordings she made from the days of her first, starry appearances when she sang as no one had sung for several generations, in music that had long been thought "dull" for lack of a Callas to revivify it.

Opinions like Leonard Bernstein's carry special weight. It was Bernstein who conducted at La Scala when Callas first sang Cherubini's "Medea" there. When it was over, Bernstein said, "The place was out of its mind, Callas? She was pure electricity."

Of Callas' reputed temperamental disposition, a recollection comes to mind to dispute her being "difficult." On Dec. 17, 1956, Callas sang in Washington at the Italian Embassy. She was a close friend of the ambassador at that time, Manlio Brosio, who remarked, in admiration of her Italian, "She not only speaks faultless Italian, but she, an American girl born and raise in New York City, speaks Italian with a pure Verona accent."

That night Callas, the diva, the volatile star, the prima donna, stood and sat in the great reception hall of the embassy for more than an hour before she sang, shaking hands and greeting the guests.

Of her inredible power as a dramatic actress, here is a true story: at her last Metropolitan Opera appearance, as Tosca on March 25, 1965, Callas, playing opposite her favorite Scarpia, Tito Gobbi, was in flaming form. In the second act, she reared up and screamed at the villainous Roman chief of police, "Assassino!!!" The impact of that one word was light years beyond anything I had ever heard in any theater.

As the screamed word ended, I heard a thud beside me.The man who had been sitting in the seat behind mine on the center aisle had fallen to the aisle foor. He was dead of a heart attack.

No critic, nor any member of the fan club of any other opera star, was ever more citical or unsparing of Callas than she was, herself. One night a high E-flat in "Lucia" did not come out the way she wanted it to. It broke wide open. Furious with herself, Callas, the instant she got off the stage, stood there and sang the high note three times over perfectly, just to prove to herself that she could.

But in the later years of her career, as she well knew, her voice showed all of the signs of the strain that she had put on it far too early when she sang those. Wagnerian roles that were much too heavy for her. The texture of the voice began to fray, a wide vibrato developed that stubbornly refused to disappear on high notes.

But Callas would not retreat or evade. When the high notes were due she went right up and into them, even when they had become increasingly painful. She had made her art incomparable, and she did not know what it was to compromise.

In her singing, as in her life there were rich lights and shadows. No one else in my experience has sung a rising or descending chromatic scale with her precision, and at the same time her gift for making it a vital, dramatic passage. Nor have any but the fewest given to the words of the most familiar opera scenes the sensitive, searching, exquisite pronunciation that Callas always achieved.

Out of her short life, her short career was a glorious one that changed the face of the opera world for the last half of this century. Few singers have done half as much.