A U2 concert, by definition, should be a musically inspiring and emotionally overwhelming experience.

Intensity, passion and glorious exhaustion form the essence of U2 live, as captured on film and on record with the 1988 release of Rattle and Hum.

Unfortunately, the musical direction and live performance style of this Irish super-group has dramatically changed in the four years since Rattle and Hum, and the band's Zoo TV production March 13 at the Worcester Centrum had neither the look or feel of a U2 concert.

Opening with eight songs from Achtung Baby and virtually ignoring their existence before The Joshua Tree ("Pride (In the Name of Love)" was the notable exception), U2 intentionally divorced themselves from their past and thus alienated and disappointed many in the crowd who prefer the simple passion of U2 past to the bizarre high-tech production of U2 present.

Even when U2 deigned to give the crowd such beloved relics as "With or Without You" and "Running to Stand Still," the hollowness of their performance and the almost begrudging acknowledgement of their history weighed heavy in the darkness surrounding Bono's spotlight.

Live performance is the true test of the strength of a band's material, and the Zoo TV concert illuminated all the subtle differences between Achtung Baby and its more worthy predecessors.

Though seclusion in a Berlin studio enabled U2 to produce the industrial grunge and searing riffs of "The Fly," the innovative blend of a wicked guitar groove with vocals ranging from gospel heights to darkly sexual depths could not be effectively reproduced in concert.

Even the best and most popular tracks from Achtung Baby, such as "One" and "Mysterious Ways," suffered in live performance. Over-familiarity from excessive radio airplay combined with the band's unremarkable and unenthusiastic presentation to make fine material almost boring.

The inclusion of the new album's less impressive material, such as the virtually pointless "Who's Gonna Ride Your Wild Horses?", seemed unnecessary and frustrating when many of the best U2 songs were left off the set list. The most disappointing and inexcusable omission was the band's failure to perform such classics as "Sunday Bloody Sunday," "New Year's Day," and "Exit".

The band performance and crowd response noticeably improved when U2 finally began to play material from past albums. Walking along a narrow platform to a small stage on one side of the floor, the four members of U2 performed an acoustical version of "Angel of Harlem" with spirited vocal accompaniment from virtually every member of the audience.

The emotional impact of U2's performance steadily increased with each selection from U2's earlier albums, reaching a climax for both band and crowd with "Pride (In the Name of Love)" the only track performed from The Unforgettable Fire.

Numerous video and television screens placed about the stage showed black and white footage of a speech from the Rev. Martin Luther King Jr. about whom some of the powerful lyrics of "Pride" had been written. The music and lights gradually faded until King's speech dominated the dark silence of the arena.

U2 made effective use of their video technology throughout the show, especially during several tracks from The Joshua Tree. Rather than simply showing close-ups of the band members and action onstage, the video presentation coordinated film clips, powerful phrases and strong visual imagery with the set list, thereby giving an added dimension to the music.

Home-movie footage of the band wandering about a desert plain in their Joshua Tree days provided entertaining visual accompaniment to "Where the Streets Have No Name."

Bright orange tongues of flame roared on the TV screens placed about the stage during "Bullet the Blue Sky," serving as a forceful visual representation of the lyrics: "Plant a demon seed/ You raise a flower of fire/ See them burning crosses/ See the flames higher and higher."