By ANTHONY TOMMASINI Edward Downes, the musicologist, lecturer, professor and critic, best known as the longtime host of the Texaco Opera Quiz heard during the live Metropolitan Opera radio broadcasts, died on Wednesday in his Manhattan home. He was 90.

The opera quiz, in which panels of three opera experts answer questions from listeners during intermission, recently began its 61st season. Mr. Downes was its quizmaster from 1958 to 1996. His mellow baritone speaking voice, laconic manner and avuncular wit made him a beloved radio personality to the millions of opera buffs and neophytes who tuned in to the Saturday broadcasts.

The questions that tend to get selected for presentation to the panel fall into two categories, Mr. Downes explained in 1996 to a reporter for The New York Times. There are the 'Who stabbed who in the third act?' questions, he said. And there are the so-called discussion questions, where everyone can jump in, which make for better radio talk. The latter type solicit opinions and recollections, not facts, Mr. Downes said, like: What ending to an opera plot would you like to rewrite? Or, What would you give Wotan or Tosca for a Christmas present?

Whatever the questions, Mr. Downes had a way of putting panelists and listeners as ease. When the experts hesitated, he would fill in the silences with teasing hints to the answers. He knew that often the most entertaining chatter came from panelists who were stumped, if he could just encourage them to laugh at themselves.

He also gracefully interjected his own comments, drawing from a wealth of firsthand knowledge. A panelist might speak of Rossini's William Tell, and Mr. Downes would mention having seen a production in Germany of the Schiller play on which the opera was based. Or, during a discussion of Britten's Death in Venice, he might share his recollections of having heard a lecture in Munich by Thomas Mann, author of the book that inspired the opera.

The sound of his voice made listeners feel he was their friend, said Michael Bronson, who produces the intermission features, speaking of his longtime colleague. The mail still comes in addressed to Edward.

Edward Olin Davenport Downes was born in West Roxbury, a Boston suburb, on Aug. 12, 1911. His father, Olin Downes, who later became the chief music critic of The New York Times, was then a critic at The Boston Post. Mr. Downes began attending operas with his father and by age 9 was an ardent Wagnerite with a passion for Siegfried. Some might assume that this daunting opera (a five-hour evening) would be too much for a child; young Edward found it a great adventure story.

When you think about it – a magical sword, killing the dragon, throwing Poppa aside, climbing fiery mountains and waking the girl with a kiss – what better stuff could there be?

In 1924 the family moved to New York when Olin Downes took the Times job. Without having completed high school, the younger Mr. Downes attended Columbia University and the Manhattan School of Music. During World War II he served in the Army, at one point helping Arthur M. Schlesinger Jr. prepare briefing books for the Office of Strategic Services, precursor of the Central Intelligence Agency. Later he studied languages and took courses at universities in Paris and Germany, but he never earned an undergraduate degree. I couldn't see why I needed one, he said. Eventually, in 1958, he received a Ph.D. in musicology from Harvard University. He was 47.

He went on to a peripatetic career in academia, teaching at Wellesley College, the Longy School of Music and the University of Minnesota. When his father died in 1955, Mr. Downes became a music critic at The Times, staying for two years until taking the opera quiz job, which offered the same pay for just 20 weeks of work. From 1966 to 1983 he taught music history at Queens College. For 18 years, starting in 1960, he also wrote program notes for the New York Philharmonic.

In 1943 he married Mildred Fincke. The marriage ended in divorce in 1954. He is survived by a sister, Dorothy Williams of New York, and four nieces and nephews.

An extensive tribute to Mr. Downes, with excerpts from his broadcasts and anecdotes from friends, is being prepared for a presentation on what is now called the ChevronTexaco Opera Quiz, Mr. Bronson said. No date has been set for that program, but a brief tribute will be read during tomorrow's broadcast of Humperdinck's Hänsel und Gretel, the first opera Mr. Downes saw as a child.

Photo: Edward Downes (Sara Krulwich/The New York Times, 1996)