Ten days ago, Patricia Orchard, a teacher of voice at the University of Lethbridge in Alberta, Canada, wouldn't allow her children to listen to jazz or pop records.

"I know they sneak and do it when I'm not around," she confided. "But I'd try to regulate their listening habits."

That, however, was before she signed up for an intensive 10-day institute on criticism in jazz at the Smithsonian Institution. Now Lethbridge has swung 180 degrees - "I'm going to let them listen to jazz, and I intend to take a course in jazz at the university," she said. "I'm determined to learn more so that I can appreciate it and even write about it.

Orchard even goes so far as to say that the jazz institute has been "the most informative two weeks in my life. They've really turned me around."

Orchard was one of eight critics - and several auditors - who finished the seminar yesterday, and she and her colleagues were unanimous in their assessment that their attitudes about jazz had changed.

Many of them had scant knowledge of popular culture. Nina Deutsch, who has recorded for Vox Records the complete piano works of Charles Ives, had never heard of Twyla Tharp, the modern dancer the media discovered with a bang last year. Several critics were not familiar with popular songs such as "Body and Soul" or "The Man I Love."

On the first day of the seminar, the critics sat impassively as Martin Williams, director of the Smithsonian's Jazz Program, compared records of the same pieces by Art Tatum and George Gershwin, Ella Fitzgerald and Gertrude Lawrence.

They found Gershwin or Lawrence's period interpretations of "Someone to Watch Over Me," stilted and Tatum's ornate melodies and Fitzgerald's "sweet" renditions quite foreign.

"I just didn't like the way he (Tatum) played," said Orchard. "It sounded like a bunch of scrambled notes."

But by yesterday, several critics had come to view jazz - and performers like Duke Ellington, Charlie Parker and Cecil Taylor - in a different light.

"You've got to screw your ears on differently," said Patrick Smith, editor of The Musical Newsletter. "Part of the problem is forgetting about the critical standards for classical music. Before I came here I thought that improvisation couldn't be as important as written work. Now I see things differently."

On hand to help the critics along were teachers such as composer-conductor Gunther Schuller, writer Albert L. Murray, pianist John Eaton, James Morris, director of the Smithsonian's Division of Performing Arts and Bernice Reagan, a consultant in Afro-American music for the Smithsonian.

After 10 days, no one should expect the worlds of jazz and classical music to merge, or the eight critics to become instant jazz experts. The purpose of the seminars, according to Williams, was to acquaint the critics with another musical tradition so that they could become better reivewers.

Will better work from the critics help jazz "What jazz needs is prestige," said Williams. "Money, recognition. These people can't supply that. We were trying to introduce a new subject and a new approach."

Most of the critics came without any knowledge of jazz. Not all were like Orchard, who said that whenever she heard a jazz or pop record on radio she would turn off the set.

Arlynn Nellhaus of the Denver Post and Allen Skei of the Fresno Bee, for example, both occasionally review jazz performances. But, said Nellhaus: "Ifound myself writing about jazz, but I didn't know enough about it."

Deutsch, a critic for Our Town newspaper in New York and a music consultant for the Joe Franklin talk and variety show, said the sessions "challenged our basic understanding of music."

Indeed, the critics were challenged from the beginning when Schuller, outgoing president of the New England Conservatory, on the first day asked any critic to pick a selection from the "Smithsonian Collection of Classic Jazz," a five-recent set racing the history of jazz.

Nellhaus picked Sarah Vaughan's "Taint' No Use," a rococo display of vocal virtuosity. Schuller asked the critic to compare the performance with an opera she might review. She then said she would compare its technical mastery to that found in the opera "Boris Godounov."

Schuller then launched into a $99;[WORD ILLEGIBLE] -minute detailed examination of the Vaughan, sporadically commenting on other days with record by Duke Ellington, Charles Mingus and Cecil Taylor.

The critics identified with Schuller, the critic's reactions. He did the same. He spoke their technical language and is an accomplished composer. Smith said, "Gunther's analysis fo Sarah (Vaughan) was excellent. It was like a microcosm going outward. He taught me how to listen to a piece from a structural point of view."

Schuller, Williams and J.R. Taylor also of the Smithsonian, examined the 12-bar blues form and the 32-bar popular song form, two structures they, were able to get the critics to hear after repeated listenings.

But they moved tentatively. Said, Williams: "One of the things they are most inhibited by is that in this music, everything they hear is something new. They reacted negatively when I asked them to evaluate a performance after one hearing.

"They said that in classical music, they could study the score, go to rehearsals - listen to Beethoven's Ninth Symphony all kinds of ways."

He laughed and said, "Then I said what would you do with Beethoven's 10 Symphony?"

Albert Murray, a writer of fiction, social criticism and cultural theory, offered the critics another approach the esthetics of American culture, and specifically Afro-American life.

He used jazz terms such as vamp, out chorus, riff and breaks, successively explaining himself by pointing to passages in some of his favorite records by Ellington and Count Basie.

Will the Smithsonian or the Music Critics Association, joint sponsors of the institute, follow up the critics to find out what effect the seminar had?

"If they behave like the jazz critics, they'll follow us up," said Williams. Every week there're articles coming across my desk from jazz critics we've had in institutes."