By Rob Hubbard
Pioneer Press

If there's a signature sound for the whole "classic rock" radio playlist that's changed so little in the past quarter-century, it might belong to Boston. The layers of electric guitars playing roughly the same line and the wailing high tenor of Brad Delp supported by a sea of harmonies: They all scream the late '70s to some or as fresh as this morning for regular listeners of the Twin Cities' most popular radio station.

The soft metal septet christened the freshly refurbished State Fair Grandstand on Thursday night with a show that was at its best when satisfying the nostalgic urges of an audience of 5,385 for material from the band's first two albums. While some bands that found stardom in that era approach their older material with noticeable disinterest, Boston seems to understand that there's a reason theirs has endured as well as it has. Sure, Delp needs a little help with the highest notes nowadays - they're often handled by fellow frontman Fran Cosmo - but the band is as conscientious as ever about reproducing its studio wizardry in concert.

And make no mistake: Boston is more of a studio band than an arena rock legend. Its sound is the brainchild of Tom Scholz, a skilled guitarist and engineer who concocted it in his basement and has since come to be known for taking eight years to finish each of the band's last three albums. Alas, most of the band's recent songs lack the anthemic hooks of its early years, and Thursday's audience responded tepidly while waiting for '70s fare to resurface.

Scholz proved that his impressive guitar licks are no studio creation, ripping through a couple of rapid- fire solos in the Eddie Van Halen vein and engaging in the band's patented piercing guitar duets with the almost equally adept Gary Pihl. However, the Boston wall of sound (employing as many as five guitars) sometimes crushed the vocals of Delp, Cosmo and company.

But, when the band tore into the pounding power chords of the "Foreplay/Long Time" medley that acted as its debut's center piece, it was more than a blast of nostalgia: It was a rich reminder of the stirring power that makes this band still a classic of "classic rock."

And for anyone who's bemoaned the ramshackle grandstand in previous years, you should be impressed by the redesign. Where once a racetrack divided artists from audience, there's now an expansive seating area fronting a stage that is set well into the infield. While the slope is slight on this "main floor" - making for inevitable standing behind enthusiastic first day ticket buyers - it's a pleasant configuration with more seats facing the stage than in the neck-craning days of yore.