When Shari Lewis leads a philharmonic orchestra through the finale of Tchaikovsky's Fourth Symphony, children are apt to get up and dance in the aisles.
''Little kids don't know it's supposed to be serious music,'' Miss Lewis says with an impish grin. ''All they know is that it's a great tune and the rhythm is terrific!''
If older brothers and sisters are along for the concert, she adds, ''they're exposed to the fact that 90 musicians playing superbly make at least as good a sound as five electric guitars.''
Shari Lewis is probably best known as Lamb Chop's mother by the generation of Americans who grew up with the wisecracking hand puppet in the early '60s. With her stylishly coiffed curls and batty black eyelashes, Lamb Chop still plays a prominent role in Miss Lewis's performances. But today, instead of berating television cameramen, she's more likely to turn her charms on the first violinists in an effort to get the attention she's so sure she deserves.
Much to her chagrin, no doubt, Lamb Chop is only one of several puppets who now share the stage with Shari Lewis. Two 5-foot, 4-inch showgirls, a 5-foot, 8 -inch Fred Astaire look-alike, and a more diminutive violin-playing kangaroo supplement the cast of characters that appear in concert with Miss Lewis and well-known symphony orchestras throughout the United States, Britain, Canada, and Australia.
The concerts are a blend of classics and comedy. ''I conduct and perform,'' Miss Lewis explains, ''and when I'm conducting, I do it very straight. I do classical works, like the overture to ''The Marriage of Figaro,'' by Mozart, or the farandole from ''L'Arlesienne,'' Suite No. 2, by Bizet.
''I never violate classical music by kidding around with it,'' she continues, ''but I do violate the tradition of classical music which says that it is stuffy and that it has to be played by musicians who are aloof. I really believe that the melodies that enchanted Mozart and Brahms and Beethoven and Chopin were folk melodies, and that they're music for the folk. I look for something that makes me say, 'Oh, I want to dance!' ''
Instead of depending on ''kid stuff,'' Miss Lewis says she tries to include material that is funny enough to make adults and children laugh. As a result, her audiences are often composed of several generations of families - her ''Sixties kids,'' their parents, and their children.
''The perfect audience is that family audience,'' she adds. ''The children hear their parents laughing, and they suddenly listen up. The adults really relax and kick off their shoes because they hear the kids giggling. And the combination makes for an audience that is relaxed and childlike and excited.''
Shari Lewis describes her symphony work as a ''delicious opportunity'' to combine all of her childhood training and dreams, including a long-held ambition to dance with Fred Astaire. Raised by a mother who was music coordinator for the New York Board of Education and a father who was the official magician for the City of New York, she was surrounded from an early age by both the classics and what she calls ''novelty entertainment.'' Any extra money in the household went toward her piano and violin lessons, and for years she expected to be a ballet dancer when she grew up.
''I danced in a number of companies as a teen-ager, but after a while I got distressed,'' she recalls. ''Although I could get into any chorus, I couldn't get out of the chorus and into solo work. And I just didn't have a chorus psyche.
''Finally, I went to Daddy and said, 'Where did we put the puppet?' and he reminded me that it was under the bed. Three months after I started in ventriloquism, I won the Arthur Godfrey Talent Scout award on TV, and I've been working ever since.''
In addition to winning five Emmy Awards and a Peabody, Miss Lewis is past president of the American Center of Films for Children, and has served as adviser to both the national board of directors of the Girl Scouts of the USA and the international board of the Boy Scouts of America. She recently finished writing a pilot for an adult television situation comedy, a movie script, and a children's book - her 22nd so far.
Although ''One-Minute Bedtime Stories'' (New York, Doubleday) doesn't happen to include a condensed version of ''The Little Engine That Could,'' that's the children's story she brings to mind as she sits poised on the edge of a conference room couch, shoes off, red hair bouncing enthusiastically, theatrical eyelashes fluttering, reminding herself to finish one sentence before starting another.
Miss Lewis started writing ''One-Minute Bedtime Stories'' 18 years ago, when her daughter Mallory was a toddler. She says she knew the importance of reading to her child, but like many working mothers at the end of a long day, she was too tired to face the 12-page adventure of the gingerbread boy. ''By Page 8, I was ready to crumble the cookie with my bare hands.''
The 20 fairy tales, legends, and fables in Miss Lewis's new book each take only a minute to read, but can be stretched out by parents asking ''Why?'' and ''What would you do if?'' questions and by referring to the zany illustrations.
''It really is essential to read to a child from the time he or she is three months old,'' she says. ''I have one friend whose five-month-old will crawl into my lap with a book and sit there staring at me expectantly. She's probably thinking, 'Someday I'm going to get this,' and in the meantime she's developing a happy association of reading with fun and attention. For her, reading is equated with love.''