CHICAGO; in concert at ParkWest; Aug. 19, one show only.The scene on the mountainside at ParkWest was more like an after-a-football-game-outdoor-stomp than a concert.

People were dancing, waving their arms, singing in unison to the tunes.

No one could seem to listen to Chicago and remain sitting. The upbeat rhythm coaxed even the most self-conscious fan into enthusiastic feet-stomping.

Chicago encouraged the let's-dance spirit by continually shifting choreography and swinging back and forth on the stage as they played their seamless ensemble sounds.

There was nothing stagnant about their performance. One song blended into the next song in an uninterrupted, easy style, building momentum and excitement.

Sassy, sultry, jazzy and brassy songs - familiar and new - characterized the charismatic mood of Chicago's Friday night performance.

The contagious energy of the group captured the audience as soon as the band stepped on stage, playing the first song, "Stay the Night." Anyone attending the Chicago performance would have thought the band was playing even its "vintage Chicago" tunes such as "Saturday in the Park" and "25 or 6 to 4" for the first time. The band exuded such energy it was difficult to believe they have performed the songs thousands of times over the past years.

While Chicago is virtually a techno-rock band now, the band stayed true to its jazz rock roots. Several old, horn-dominated hits were played, including "Does Anybody Really Know What Time It Is?" and "Beginning."

Instead of relying on gimmicky "We-love-you-Utah" type lines shouted at the audience, Chicago members depended upon their music to build rapport and communicate with their fans. It worked.

This ageless band has obviously captured the devotion of young fans who responded with wild applause to the love ballads that made Chicago popular in the 60s and 70s and also to new songs on the latest Chicago 19 album.

Longtime Chicago fans will notice the subtle, yet telling, stylistic shifts of Chicago 19 - most notably a harder melodic edge emphasizing the vocal arrangements of Bill Champlin. Champlin also does much of the lead vocal work along with Jason Scheff and Robert Lamm.

While the unique voice of Peter Cetera is missed - the instrumental background sometimes overpowers the vocalists - Chicago has maintained its appeal and unique sound.

The concert was retrospective of their careers. This is a band that has served as the soundtrack to the lives of a whole generation, selling more than 80 million albums and having a list of chart-topping singles longer than the entire repertoire of many other groups.

Their music cuts across the rock 'n' roll spectrum with its heavy metal guitar, tight synthesizer segments, drum and flute solos, the hot brass sound of a big band and the full harmonies of the prerequisite pop ballads.

Trombonist James Pankow, who is responsible for all of the arrangements of Chicago's music, credits the group's chemistry for much of their success. It is rare for a group to be as popular as Chicago for so many years, he says.

"Longevity is rarely achieved in the rock and roll business. This stands as a tribute to the fact that Chicago's approach to music has withstood the march of time. It's gratifying to be part of such a legacy," said Pankow.

The band members in Chicago are all accomplished musicians: Chaplin plays the keyboards and guitar; Lamm, the keyboards; Walt Parazaider, the woodwinds; Lee Loughnane, the trumpet; Danny Seraphine, the drums; and Scheff, the bass.

Their combined talents created a professional, polished, electrifying performance at ParkWest for their Utah fans.