Sarah Brightman at the Forum

Judging by the evidence presented Saturday night at the Forum, Sarah Brightman -- it seems safe to assume -- is unfamiliar with the old showbiz adage, “Always leave ‘em wanting more.”

Best known for originating the role of Christine Daaé in ex-husband Andrew Lloyd Webber’s “The Phantom of the Opera,” Brightman has over the last two decades become one of the biggest names on the classical-crossover scene. And at the Forum, the English singer-actress wasted no opportunity to demonstrate that stardom in that world needn’t be entirely unlike stardom of the top 40 variety.

There was simulated synchronized swimming. There was an enormous video screen flashing 3-D holograms. And backstage somewhere, there was a bottomless costume trunk that contained at least one pair of white thigh-high boots.

There was also, I’m fairly sure, a bit of music -- though singing hardly seemed like the focal point of the two-hour show, the next-to-last date of a North American tour in support of Brightman’s two 2008 albums, “Symphony” and the holiday-themed “A Winter Symphony.”

Brightman’s technical ability is a thing of fact: Amplified by a sound system jacked to levels seemingly unchanged from Metallica’s Forum shows last Wednesday and Thursday, she wailed through “Phantom’s” title song and found unexpected menace in a moody trip-hop reading of “What a Wonderful World.” (Her attempt to uncover the hidden depths of “Dust in the Wind” by Kansas proved less fruitful.)

Still, however impressive Brightman’s singing was Saturday -- though this was an arena show, she didn’t shy away from classical material -- her performance lacked energy and character, especially considering the technological spectacle of it all.

Duets with Mario Frangoulis and Fernando Lima (two thick slices of poperatic beefcake) seemed sexless and cold. “I Believe in Father Christmas” felt like an apology rather than a pronouncement. “Symphony” never broke out of its syrupy soft-rock rut.

On her appealingly over-the-top records, Brightman and her collaborators successfully distracted us from that personality deficiency by pooling every sonic color and texture; it’s music that never stops becoming something else, which is perfect for Brightman’s shape-shifting voice.

With only seven musicians, though, Brightman’s backing band, stashed for the most part behind that video screen, couldn’t cushion her in the same way at the Forum, where synthesized strings lent the music a cheapness at cross-purposes with its intended romance. (Fortunately, that didn’t detract from the kick to be had by watching them headbang during “The Phantom of the Opera.”)

The result was dull without feeling virtuous, tacky but not particularly fun.

In her attempt to give her audience everything all at once, Brightman left out the one element people actually came for: herself.

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