At the ripe old age of 23, the Growing Girls have spent more than half of their lives singing four-part harmony. And along with the good food and fresh air of their native Sweden, this upbeat music has made self-assured, exciting young women of them.

The Growing Girls are the 1989 champions of Harmony International competition, and as such are Queens of Harmony, entitled to wear the rhinestone tiaras given to all first-place winners and join the organization's Coronet Club.The four are Anna Bonnedahl, baritone; Suzanne Frolin, lead; Naima Roos, bass; and Malin Lindgren, tenor. They speak "American English" without discernible accent - a requirement for success in barbershop competition. That hasn't been hard for them to pick up, they said, with coaching, listening to lots of American music and concentrating on eliminating the clipped British accent of their schooling.

Their barbershop addiction began with Anna's and Malin's parents, who belonged to barbershop singing groups. The choral tradition is strong in Sweden, said Malin, where 10 percent of the people sing in choirs. "And where people love to sing, barbershop catches on readily. There are 12 chapters of Harmony International in Sweden, five of them around Stockholm."

Anna's mother, Britt-Helene Bonnedahl, who leads the prize-winning Ronninge Chorus (fifth place last year), knew that Anna was fascinated with barbershop singing and thought, why not get a girls' quartet together?

The four were all attending a performing arts school, where they continued through their high school years. "It's been a big advantage to have training in classical music," said Suzanne.

They debuted at age 11, and they remember the first song they ever sang together - a gospel number, "Do Lord (do remember me)." They were an immediate success and began singing in barbershop shows around Stockholm, at company parties and other social events.

"My mom trained us, hauled us around and did the talking," said Anna.

When they won first place at last year's convention, they quit their jobs to concertize. Have they made enough to support themselves? "Barely," they agreed, with a general laugh.

But their year of touring and enjoying their victory has been important to them. They toured America last summer, and are in the midst of a second tour, working out of Louisville, Ky., for guest appearances in Providence, R.I.; St. Joseph, Mo; Minneapolis; Portland, Ore.; and San Francisco.

Will wedding bells break up that old gang? It seems inevitable, since Naima will be marrying an American from Louisville in January, and Anna is engaged to a Swedish man.

What have been the lasting effects of a youth spent in barbershop singing? All positive, they agreed.

"Though we spent big blocks of time practicing and performing, I never felt that we missed a thing growing up," said Malin. "We always had many friends outside our quartet."