Welcome back, Joni Mitchell. You've been away long.

Los Angeles audiences have been waiting for Joni to appear in concert for a long time. She was set to play Universal last year but canceled.

Luckily for her fans, she kept her Amphitheater dates, this time opening last night in the first of two concerts with a tour de force performance. When she addresses the audience with "So how are ya L.A.? Seems like a long time since I saw you face to face," her fans welcome her loudly.

The Canadian songwriter/performer, who admits to middle age, has grown better as she's grown older. She's a performer with a mystique and aura about her even though her songs are personal explorations of her own life experience. Yet yet she holds nothing back on stage as she performs with all the energy an audience could hope for. She never stops pushing. She's a good model for all those young girl rock 'n' rollers coming up.

She's a musician whose songs are uniquely her own - one of those artists who came up in the '60s by writing for other artists. An early hit was "Both Sides Now" for Judy Collins.

Her renditions were infinitely more interesting, much more rhythmic and less canned. And although her material continued to covered by other artists, she ultimately developed a following of her own.

But she was always a different breed. Although her songs were very personal, her musical modes were always changing. She's explored all the avenues from pure pop to avant-garde jazz adding lyrics to the works of the late, great Charles Mingus.

And now in the '80s, she's matured into a virtuoso artist whether she's playing a variety of guitars, strumming a dulcimer-type instrument on her lap, sitting at the piano or standing without any instruments in front of the mike singing.

She's a performer whose songs tell stories, whose material conjures unlikely images her lyrics in the middle of conversations from "Free Man in Paris"- "The way I see it, he said, "You just can't win it... Everybody's in it for their own gain, You can't please 'em all."

Joni's program is a good mix of her musical range. Opening with "Free Man," she mixes oldies with offerings from her latest release, "Wild Things Run Fast" (Geffen).

Her newer songs include the title song, "Chinese Cafe" at the piano, "Solid Love," "You're So Square," "You Dream Flat Tires" and "Love." Old favorites are "Radio," a beautifully haunting "For Free" at the piano, "Big Yellow Taxi," "Case of You," "Help Me" and a hip-swaying, rousing "Robbery."

She closes the regular part of her program playing solo acoustic guitar on "Both Sides Now" giving the lyrics a wiser and more experienced interpretation then ever before. Then she plays herself off stage.

Back on stage with a drink and cigarette, Joni and company pay tribute to Marvin Gaye with a swinging version of "Grapevine" for encore number one, followed by "Street Light" off the new album.

And back in the solo spotlight, she closes the evening with a slow, bluesy back at "Woodstock," filled with feeling and irony. As she moves to the apron of the stage away from the mike, the crowd rushes to greet her - it's a strange mood as she sees them for the first time. And again, she keeps playing into the wings and she's gone.

Mitchell is blessed with a dynamite band featuring Vinnie Colaiuta on drums, Russell Ferrante on keyboards, Michael Landau on lead guitar and her husband, Larry Kline, on bass.

Also adding a definite note of beauty and class to the evening are seven gorgeous panels displaying art work by the star herself, hanging overhead lit with great artistry by an unknown technician.