Usually, when you plunk down your $8.50 for a rock/pop concert ticket, you have a pretty good idea what to expect at the show. Most artists typically perform familiar renditions of their hits plus a handful of lesser known songs from their latest album.

There are rarely any big surprises at concerts, unless you're dealing with a risk-taking eccentric like Bob Dylan, who threw a real curve last year by drastically rearranging many of his old tunes for his concert tour.

Joni Mitchell, another risk-taking eccentric, has been tossing curves for the past few years. On her last four albums, the celebrated Canadian folk and pop singer has been flirting with jazz. The commercial and critical reaction has been mixed. And, quite frankly, few of her longtime fans really knew what to expect when Mitchell walked onstage Sunday night at the Minneapolis Auditorium with a quartet of crack jazz musicians.

Well, it was a pleasant surprise. The concert was terrific.

Jazz and the new Joni

Three years ago when Mitchell last performed in the Twin Cities, she had just begun her serious foray into jazz and her performance seemed tentative. Sunday night, she played with unflagging confidence from the first song, a cacophonous rendition of "Big Yellow Taxi," to the finale, a jazzed-up, solo reading of "Woodstock."

Mitchell's concentration seemed intense. She did not speak to the near-capacity crowd of 7,000 persons except to respond to a heckler and to introduce the members of her band. Her silence seemed calculated and purposeful. She is no longer the innocent folkie singing eloquent, melodic confessionals; rather, she is an articulate jazz musician.

It was evident Sunday that Mitchell's musical development has caught up with the sophistication of her lyrics. At age 35, she has blossomed from a songwriter into a composer. The arrangements are now as important as the words. And her accompanists onstage made a difference.

Mitchell has surrounded herself with players who not only work well as an ensemble but are fascinating soloists. Michael Brecker's hot, soulful saxophone work was a favorite with the crown. The always tasteful Pat Metheny consistently demonstrated why he is considered the brightest jazz guitarist to surface in years. Animated Jaco Pastorius' gimmicky bass solo was well-received but he was more effective in the ensemble work as were drummer Don Alias and keyboardist Lyle Mays.

Mitchell, who in past concerts has divided her time between acoustic guitar and piano, played electric guitar almost exclusively. Oddly, her recent songs are neither guitar-oriented nor especially melodic. When she sang a couple of selections from "Mingus" (her new album and first pure jazz record), she simply stood at the microphone stand, dancing to the music. Her attempts at jazz-styled singing seemed more successful in concert than on "Mingus." "Goodbye Pork Pie Hat" was sultry, swinging blues that showed the new-found facileness of her vocal range.

Most of the material Mitchell performed in her well-paced 105 minute concert was drawn from her last five albums. In most cases, the arrangements were different from the recorded versions. And, in almost all instances, the new treatments were effective. Especially noteworthy were "Dreamland," on which the singer was accompanied only by congas, sticks and cowbells, and gospel version of "Shadows and Light" featuring the Persuasions, the a cappella group that had opened the concert with a stunning set of pop, soul, and gospel tunes.

To the disappointment of some fans, Mitchell did not perform her best known songs, "Both Sides Now" and "The Circle Game," classics from her late '60s folksinging days. Only during the encores - "The Last Time I Saw Richard" and "Woodstock" - did she harken back to the old days. It was clear that Mitchell is seeing life from a different side now. And most of the concertgoers were surprisingly delighted to discover this new side.