She was still blowing a hot tenor sax in 1981 on Johnny Carson's "Tonight Show" and, later, on the NBC sitcom "The Golden Girls."
"The first time I picked up a sax, I said, 'This is it!' I loved the feel of it -- free and loose," she said in a recent interview. And the instrument played a starring role in her 95-year career.
Gilbert, who was born in Iowa and lives in Studio City, is nearly 102. But her memories remain as fresh as the day in 1912 when she made her stage debut, dancing a Scottish fling at age 7.
By the time she graduated from a Sioux City, Iowa, high school in 1923, she was playing the saxophone in her five-piece, all-girl band.
She arrived in Hollywood in 1928, at age 23, playing in hotels, nightclubs, radio, movies and television.
During the Depression, "as a joke, two friends of mine, male musicians, dressed in drag trying to get a job with my band," she said. "It was just like in that movie 'Some Like It Hot,' " starring Marilyn Monroe.
Although it was rare for male musicians to dress as women, it wasn't unusual for a woman to dress as a man to play in an all-male band that wouldn't accept women, Gilbert said.
"It wasn't until World War II that women musicians were accepted to play with male bands," she said.
So women played on their own. Jeannie Pool, a music historian and cultural preservationist who wrote and produced the new documentary "Peggy Gilbert and Her All-Girl Band," said: "There were so many all-girl bands in the 1920s and 1930s that one group of women got together to spoof the all-girl bands, calling themselves the 'Kitchen Band.' They played with eggbeaters and spatulas, anything they could find in the kitchen drawer.
"But Peggy has seen it all, done it all and has plenty to say about life and music," Pool said.
Music is entwined with Gilbert's DNA. Her father was a violinist and conductor of the Hawkeye Symphony Orchestra in Sioux City; her mother was an opera singer. Born Margaret "Peggy" Knechtges on Jan. 17, 1905, she had a piano waiting: Her parents bought it for her before she was born.
When she was 7, a Scottish minstrel named Harry Lauder hit town for an engagement. Gilbert's third-grade teacher had taught her and six other girls to dance the Highland fling in authentic costumes. Lauder was so impressed that he took the girls along on a summer tour through the Midwest. The other performers looked after the girls.
"My parents didn't worry," Gilbert said. "They knew the business required traveling and believed I needed to learn how to do it. We loved it."
Soon, she was playing the piano with her father's string and wind groups. But her heart was set on playing the saxophone. Her brother played the drums, and her high school boyfriend played the sax.
"Not that I wanted to best him," she said, "I just liked it."
But girls weren't allowed to play wind instruments in the school band -- only the "womanly" violin, piano and harp. So she took sax lessons from a local bandleader.
She played her first sax gig with her brother Orville's band in 1926, when she was 21.
Soon she started her own band, the Melody Girls. They played for club dances and hotels in the Midwest. "I wasn't trying to be a star, just make a living," she said.
In 1928, her father died and so did her sister-in-law, leaving Orville with three small children.
It was up to Gilbert to help support and raise her extended family. So she packed up her mother and grandmother in her Dodge and moved to Los Angeles, where an aunt lived.
Orville followed with two of his three children. The youngest girl stayed behind to be raised by her maternal grandparents.
In Los Angeles, Margaret "Peggy" Knechtges changed her name to Gilbert, her mother's maiden name. No one could pronounce or spell Knechtges.
During the Depression, she and her family lived in the Pico-Union area in a one-room apartment with a Murphy bed.
Gilbert organized bands for the motion picture industry. Back then, female musicians were expected to sing, act and dance in chorus lines.
"At one audition, a producer made us lift up our dresses. He didn't care who played what, it was who had the best legs who got the job," she said. "It was degrading, but we needed to eat."
Gilbert and her band, which changed names often, played at famous landmarks in Southern California, including the El Mirador Hotel, Cocoanut Grove, Garden of Allah, Club New Yorker, Palomar and Zenda ballrooms.
Gilbert conducted, managed, played and wrote her own music and designed the band's apparel.
"One costume had these black satin pants, and we had to back along the walls onto the bandstand because all the seats of our pants had been patched," she said.
One of Gilbert's more unusual engagements was a stint in Hawaii from 1933 to 1934. En route, aboard ship in the middle of the Pacific, the musicians learned they had been booked to play for a three-ring circus.
"If we could have walked home, we would have," Gilbert said, they were so disappointed.
But they loved Hawaii. And while touring the islands, Gilbert fell in love and became engaged. But her fiance died of a heart attack just before their wedding.
Back on the mainland, the group played at trade shows, policemen's balls and fundraisers. Her most memorable gig was kicking off "Hollywood's Second Swing Concert" in 1937 at the Palomar ballroom with big band stars Benny Goodman, Louis Prima, Ben Pollack and Les Hite.
In 1938, her group, then called "The Early Girls," played live on radio station KMPC in Beverly Hills, six days a week, from 7 to 8:30 a.m. With a talent for improv, Gilbert dueled male musicians.
She could hold her own and more -- which is why a 1938 article in the musicians union magazine infuriated her. Its title: "Why Women Musicians Are Inferior."
She responded with an article detailing the degrading discrimination that female musicians faced. To her chagrin, the magazine published her response under the headline: "How Can You Play a Horn With a Brassiere?"
During World War II, Gilbert joined an all-female USO show. Transported by plane and dogsled, they entertained soldiers stationed in Alaska. They also visited the wounded on hospital ships, holding back tears. "We had to keep them laughing," she said. "I even played two clarinets at the same time."
Gilbert married a soldier who was a sound engineer, but they divorced soon after the war.
Like thousands of other female workers, Gilbert and her band were out of a job when the war ended. "We were fired without any notice," she said. They were told, "You girls, you've got to move over and give the boys back their jobs."
Gilbert continued to perform and manage bands. She also worked for Local 47 of the Musicians Union and wrote a column for the union paper.
In 1974, at age 69, she organized the Dixie Belles, another all-female band. They played through the mid-1990s, recording Dixieland jazz for Cambria Records. They were featured on several sitcoms, including Ellen DeGeneres' "Ellen" and "Home Improvement."
By her 100th birthday party, Gilbert could no longer play the saxophone -- but she could still sing. She belted out "It Had to Be You" to her longtime friends, including actress Lily Tomlin.
"Jazz will never go out of style," Gilbert said. "We don't make the money like the rock bands, but they're overpaid and ride around in limos. We were lucky to get rides in station wagons."
Still, Gilbert says, music keeps her young.
A free screening of the documentary "Peggy Gilbert and Her All-Girl Band" will be held Oct. 7 at 3 p.m. at the Professional Musicians, Local 47 building, 817 Vine St., Hollywood.