It took only five notes for the judges to suspect a fraud at the International Violin Competition of Indianapolis, one of the world's leading music contests.

Blumita Singer, 26, of Sao Paulo, Brazil, was admitted to the competition on the strength of an impressive audition tape -- the first movement of Mendelssohn's Violin Concerto -- which she said she had recorded with "a provincial orchestra." It was "extraordinary," said Thomas Beczkiewicz, executive director of the competition. "It was so brilliant that the screening committee said she must be accepted."

But after hearing her play in person in a preliminary round Sunday, the jury concluded unanimously that the violinist on the tape could not be the one in front of them. She was the first eliminated in a process that must reduce 53 contestants to 16 for the semifinal round beginning tomorrow. Six finalists will play concertos with the Indianapolis Symphony, and the finals will produce three winners on Sept. 16.

"It was not we who unmasked her," said Beczkiewicz. "She unmasked herself. ... When you have 10 of the most expert violinists in the world, you cannot fake anything. ... They were absolutely unanimous after hearing only five notes." Some members of the audience walked out while she was performing.

"It was quite a surprise, amid the outstanding quality here, to hear a contestant playing below a student level," said Yugoslav violinist Igor Ozim, vice president of the jury. He said that Singer's performance "verged on the ridiculous," with "problems of intonation, sheer lack of skill, no vibrato, no memory -- she had innumerable memory slips... .

"Then we listened to her audition tape, and it was the absolutely unanimous opinion of the jury that it could not have been the girl who played here. She faked her way in, and that means that some worthy person who should have been admitted to the competition was left out."

Ozim spoke briskly yesterday in the middle of a busy day that began with the cut to the semifinalists and would end with a recital by four of the judges: Ozim, Emar Oliveira, Mihaela Martin, who won the gold medal in 1982, and Hidetaro Suzuki, winner of the Montreal competition and concertmaster of the Indianapolis Symphony.

Two mysteries remained after Singer left the competition, still protesting that it was her tape: where she had gone and who was the violinist on the tape. "Blumita is not here. She is in Indiana," said a woman who identified herself as Singer's mother, answering her phone in Sao Paulo.

As for the cassette, Ozim said its sound quality would "not ... allow us to say whether it was taken from a recording or from a live performance with someone in the audience using a hand-held cassette recorder."

Beczkiewicz said the tape "was probably made from a very old recording. The orchestra is indistinct, with an obvious focus on a violinist of very high caliber." He added that at first it was thought impossible to say who was the actual violinist, "but we are beginning to think that, given a few days to look into it, we might be able to come up with a name."

One good result of the incident, Beczkiewicz said, "is that it will call attention to the extraordinary level of quality in this competition. By sheer contrast, a performance like Ms. Singer's underscores this."

The competition began earlier this year with a preliminary screening committee listening to nearly 200 tapes from 25 countries and narrowing the competition down to 53 preliminary contestants from 19 countries. Ironically, Singer's name was first on the official list of accepted participants because her native country, Brazil, came first in alphabetical order. The largest number of participants (20) came from the United States, but China and Japan had five contestants each, and there were three from Czechoslovakia and two from the Soviet Union as well as one each from Bulgaria, Poland and Romania.

This is the third time the competition has been held (it began in 1982 and takes place every four years), and the first time it has had participants from the former Iron Curtain countries, but already it has reached"When you have 10 of the most expert violinists in the world, you cannot fake anything... . They were absolutely unanimous after hearing only five notes." -- competition director Thomas Beczkiewicz a stature in the world of violinists comparable to that of the Cliburn competition among pianists. The prize fund is more than $60,000, with a $20,000 first prize, plus a gold medal, more than 75 concert engagements, and recording contracts with Koch International Classics for all three finalists. The gold medalist also wins the most elusive of all prizes, a contract with a European concert management agency, Hans Ulrich Schmidt.

In her application submitted with the tape, Singer said she studied at the Manhattan and Juilliard schools of music in 1982. Among her teachers she listed some violinists of towering stature, including Pinchas Zukerman, Gidon Kremer and the late Henryk Szeryng. She also claimed to have won several other awards, including first prizes in the 1983 Fritz Kreisler Talent Award and 1975 National Young Soloists Competition.

"We can see now in retrospect that it {her application} was put together in bits and pieces," Beczkiewicz said. "She did register at Juilliard and attended some classes, but never got a grade, and she did apply to the Tchaikovsky Competition. Zukerman and Kremer don't teach, but she may have attended a master class or two."

Choosing Singer was part of "a very honest effort to search out those who are less known," Beczkiewicz said. "I don't want to discourage the screening committee from taking a few risks."

To prevent cheating, he said, future applicants may be required to submit proof of the authenticity of their tapes.