A double feature is in store for "pop" fans attending the Mississippi River Festival at Southern Illinois University, Edwardsville, Monday -- Joni Mitchell and Arlo Guthrie. The show will begin at 8:30 p.m.

Born Roberta Joan Anderson in 1943 in McLeod, Alberta, Canada, Joni Mitchell attended public schools in Saskatoon, Sask., and, bent on a career as a commercial artist, enrolled in the Alberta College of Art in Calgary. to pass the time she took along a ukelele.

After mastering some chords and a few traditional ballads, she found she could earn extra money by singing and got her first job in a coffee house called the Depression.

As time went on, she found she enjoyed singing more than painting and made a trip to the Mariposa Folk Festival in Ontario. On the way she wrote her first song, a blues number called "Day after Day," timed to the clacking of railroad wheels.

She didn't return to Alberta but found work in several Toronto coffee houses and continued to write songs. In Toronto she met and married Chuck Mitchell in 1965. A year later she went to live with him in Detroit, but the marriage was dissolved soon after.

Joni continued appearing in Detroit clubs, then went to New York where Reprise's Andy Wickham discovered and signed her.

The 25-year-old blonde has written more than 60 songs. A critic said of her, "She is a beautiful woman. her voice and her acoustic guitar are free, pure instrumentals in themselves; there is an additional beauty in the way she uses them to convey such a full range of idea-emotions."

Sharing top billing with Miss Mitchell is Arlo Guthrie, who has been singing all of his life. He began singing professionally in February, 1966, and his rise to fame began with his narration of the famed "Alice's Restaurant" at the 1967 Newport Folk Festival.

Son of the oft-eulogized folk guru, Woody Guthrie, Arlo was born in Coney Island, N.Y., July 10, 1947. He has made public appearances throughout this country, in Canada and in Japan.

In December he played at Carnegie Hall and was called back for three encores. Music has always been a part of his everyday life and after spending six weeks in college in Montana, he decided he wanted to spend his time writing songs and singing them.

He dropped out of college and since then has been writing, singing and playing guitar.