The weather may have been unseasonably cold Tuesday night, but the audience at the Blossom Music Center couldn't have been warmer to folk-rock singer Joni Mitchell.

For a girl who taught herself to play guitar from a Pete Seger (sic) song book, she's not bad.

Bursting onto stage with an energetic version of "The (sic) Big Yellow Taxi," she set the mood for an evening of good times and old favorites.

Wearing jeans and a dark blazer with a red flower pinned to the right lapel, she allowed her strange, rhythmically displaced music to cast its haunting spell on the crowd.

ALTHOUGH the subtleties of her poetic lyrics and musical idioms were hard to appreciate over the less-than-perfect amplifying system, her energy and distinctive singing style were unmarred.

Her angular face, with its hollow cheeks framed by slightly frizzy, shoulder-length blonde hair, seemed to reflect the intensity and sincerity of her music. Neither her face nor her voice are particularly beautiful by most people's standards, yet both are stunning on her.

She is not a gushing, gee-I'm-glad-you're-here performer who loosens the audience with jokes and smiles. In fact, she spoke only to announce the members of her six-man back-up group. But like Jackie Onassis, the more aloof she remains, the more people are attracted to her.

And this audience sure was attracted. They threw her enough flowers to fill a funeral home and cheered long enough to drag four encores out of her.

THE CROWD, made up mostly of gentle-looking people in their twenties, lit lighters and matches, stood on chairs, and pleaded for more. She quietly made her way back to the stage after each round of riotous applause and knocked them out again.

After singing "The Last Time I Saw Richard," and two up-beat songs with the help of her warm-up group, the Persuasions, she ended the encores with a long slow version of "Woodstock."

Though the Woodstock rock festival occurred 10 years ago this week, Ms. Mitchell's performance brought back a touch of its beauty.

For two hours, people forgot about the weather and traffic jams to concentrate on good music and good feelings.