Though it was smaller than many of the groups he's employed, especially during the "Graceland" era, the eight-piece backing band was top-notch as always, with special kudos to the brilliant Steve Gadd (whose parts were needlessly duplicated by a second drummer).

And though the strange and atmospheric sounds of his recent Brian Eno-produced album "Surprise" seem to have thrown some listeners for a loop -- Variety euphemistically described it as "underperforming," which is code for "flopping on the pop charts" -- the unusual, serpentine arrangements of songs such as "How Can You Live in the Northeast?," "Father and Daughter" and "Outrageous" sprang to life onstage, providing some of the most exciting moments Monday night at the Rosemont Theatre.

Nevertheless, something was just ... a little off.

"Turn up the vocals!" one frustrated fan yelled after the first four or five songs, and the soundman eventually complied. But the problem wasn't the audio quality; it was the singer-songwriter's lack of commitment and focus as to what he was trying to do.

Seemingly taking a cue from his a fellow '60s icon and folk legend Bob Dylan, who rarely plays his best-known songs the same way from tour to tour or night to night, Simon reworked the arrangements of many of the baby boom's most beloved pop anthems. But he didn't go far enough: Things were changed just enough to sound lackluster, off-key, out of time or just plain wrong.

The words for "Me and Julio Down by the Schoolyard" and "50 Ways to Leave Your Lover" were slurred together. "The Only Living Boy in New York" was injected with inappropriate bombast. "Slip Slidin' Away" slid right off the rails. And even the title track from his still relatively recent "You're the One" (2000) was burdened with new, odd and jarring doo-wop interludes.

The audience responded most enthusiastically to the rollicking grooves of "Cecilia" and "Diamonds on the Soles of Her Shoes," where the band's layers of percussion and three or four intertwining guitar parts created an irresistible polyrhythmic undertow. But even during these songs, Simon hedged his bets, goosing the fans to their feet by turning on the house lights in a bit of manipulative forced enthusiasm.

For all his flamboyant arm-waving and occasional attempts at a little soft-shoe shuffle, the 65-year-old artist has never been a particularly inspiring or personable stage presence. You often get the impression that he'd rather be anywhere else, and this attitude combined with the musical miscues to create a vibe as soggy and sullen as the dreary weather outside.

Simon might have been giving us a clue that he's reconsidering the art-rock direction of "Surprise" by his choice of an opening act.

Jerry Douglas' bluegrass instrumentals are about as far away from the headliner's current sounds as any genre could be, but the accomplished guitar and dobro player and his four backing musicians delivered a strong set that was much more successful in its own unexpected detours, especially when the group reinvented Weather Report's jazz fusion ballad "A Remark You Made" with a bit of low-key back-porch pickin'.