Whether drawn by nostalgia or by interest in her new material, a capacity crowd filled Barton Hall last night to hear Joni Mitchell. and she brought them to their feet by the time she was through.

She played nearly all of the songs from "Court and Spark." her new album whose release occasioned her current tour, skew with a smattering of songs from her older albums, in the course of her 22-song show (that's what I call a concert).

Her back-up band opened the program with five pieces of their own. Tom Scott, sax and woodwind player with Mitchell on earlier albums, led the "L.A. Express" - a bass, a guitar, drums and electric piano. Their sound was pleasant and coherent, but their solos and improvisations cautious, and only occasionally interesting - in a fast piece called "Vertigo." and in a handsome version of an old Coltrane number

Someone once said that jazz is repetition, repetition, and then coming off that repetition. With L.A. Express, one wished for less repetition and more coming off the riffs they sometimes seemed too attached to. Yet their very lack of assertiveness as soloists made them later a good back-up band. with Scott's winds especially nice.

Dressed in slinky orange. Mitchell opened her show with earlier songs, "This Flight Tonight" and "You Turn Me On, I'm a Radio," from albums "Blue" and "For the Roses." One often hopes at a concert that songs will sound just like the record. but would really be disappointed if they did. With this band, and with the vocal variations she made herself I which showed the influence of Jackson Browner, her older songs did sound different, and not completely smooth at first.

But the next three songs "Free Man in Paris," "The Same Situation," and "Just Like This Train" - were from the new album and worked out very well, as did the rest of the program. A bluesed-up version of "Woodstock" closed the first half, and was the first time the sound difference from the recording was satisfying.

Mitchell's voice seemed newly full and forceful, and she did less old-style sliding and more aggressive attacks on high notes. She even seemed to parody her own old ways. the kind of yodeling motif of some of her earlier music, when she echoed some high-pitched guitar slides at the end of "You Turn Me On."

Playing fine guitar. as well as piano and autoharp, she was throughout an agile musician. and it is only in watching her unorthodox tunings and untunings that you can see just how musically intricate her songs are.

This time in electric purple, she opened the second half solo and did a few older songs, including the popular "Big Yellow Taxi." After that number, catching her precarious halter tie in her guitar, her guitar in her hair, and thinking she might need scissors to get free, she made her first verbal contact of the evening with the audience. Through the first half, the audience was peculiarly respectful for a Barton Hall packed to the gills, but she didn't talk to it, and beneath the respect was a certain coolness. But the patter that followed her near accidental-strip - "Gypsy Rose Lee really had it down, just pull a string or something.. " - won the crowd over, and she never lost it afterward.

She told stories before "People's Parties" and "For the Roses" about the scenes that spurred those songs. and let fall a nice piece of self-irony when she called '`For the Roses" one in a "continuing series of rejection-of-show-business songs .. I'm such a hypocrite." She played another one later. "For Free" from 'Ladies of the Canyon," and nearly a dozen more spanning all six albums, notably "Cold Blue Steel and Sweet Fire," which for my money is the finest piece musically she has done, as well as some good numbers from the new album, like "Help Me" and "Car on a Hill."

Fooling the audience for a second by starting quite unlike the recording. she closed her set with the current single hit, "Raised on Robbery." which, once recognized, brought the crowd clapping to its feet. Storming applause and lighted matches brought her back, though, to do "Blonde in the Bleachers" and "Twisted," a song about psychoanalysts in a swing rhythm more like the Pointer Sisters than like anything Mitchell's ever done before.

But then. it is her versatility that is most impressive. She left a justifiably happy crowd at Barton.