Making sound visible is a tricky business.

Even in halls such as the Musikverein in Vienna, intended primarily for concerts, not for plays or operas, seats still face the stage for a reason -- we like to watch musicians playing. But while most classical music ensembles could stand to make their visual performance a bigger part of the listening experience, there is a point past which they start to interfere with music. A concert Monday night at Carnegie Music Hall by the contemporary music ensemble Eighth Blackbird did just that. It stepped over the line or, at the least, awkwardly walked it.

Largely a purveyor of traditional quartets, it's not often that the Pittsburgh Chamber Music Society brings in a group dedicated to contemporary art music. I applaud it for booking Eighth Blackbird, which only the night before won a Grammy for its latest CD, "Strange Imaginary Animals." Via its recordings, I have admired this sextet of violin, cello, flute, clarinet, piano and percussion for years; it has been one of new music's greatest advocates.

But lately the group of Oberlin alumni has ventured into that seam between rock and classical, determined to make music more accessible with more driving, minimalist fare and a compelling visual presence. Monday night, their clothes were trendy and they moved about the stage while performing. While it might have been a pleasant novelty to some in the audience, to me the shift was a disappointment. In Eighth Blackbird's Pittsburgh debut, it either meant the music accompanying the visuals lacked substance or the group's movements distracted from the music.

"Musique de Tables" by Thierry De Mey was a case in point. Three musicians hitting everyday objects can be amazing. Witness John Cage's "Living Room Music." But De May's piece, in a dark hall with only three lights shining down on the players banging on an amplified table, was more choreographed hand play than a rhythmic tour de force. Hands struck the table sometimes on the tips of fingers, sometimes with the fist, while sweeping gestures were coordinated. It looked good, but with the limited timbre possibilities of a table, rhythm is key and the work never built much rhythmic complexity.

Frederic Rzewski's "Pocket Symphony" is a standout work that the group has performed for years, but the group undermined it by moving all over the place. Eighth Blackbird appeared to be overly concentrating, like a bunch of classical musicians trying much too hard to look like rockers. They didn't seem to be relaxed or look as if they were having a good time -- the one thing pop and rock acts know is crucial to movement on stage.

It's understandable. "Pocket Symphony" is a ferociously difficult work, in six movements each featuring one of the instruments. With little stage presence among them -- especially when they tried to perform the treacherous pointillist parts spread across the wide stage -- it was uncomfortable to watch. While Lisa Kaplan's piano solo was a marvel and clarinetist Michael Maccaferri presented a sumptuous timbre in his soloing, too much worrying about choreography hindered the group's music-making. And it took the fun out of a work that has parts for a jaw harp and a trash can!

But things really got awkward in the second half.

Martin Bresnick's "My Twentieth Century" is a setting of a poem about the search for closure, with the repeating line, "My brother died in the 20th century." Bresnick's minimalist music is more or less background to the various pairs of performers as they put down their instruments and recite lines of the poem to each other. Eighth Blackbird instead projected the readings onto an onstage screen, an attempt at a mini-art film that came across as amateurish. Better to have just read the poems straight to the audience.

In Tamar Muskal's "Mirrors," visuals all but squeezed out the music. The piece calls for interaction between the musicians and a video camera that manipulates the images, created by artist Danny Rozin, on screen. If you want to call the mugging for the camera and the silly poses an overly obvious attempt to be chic, go ahead. I call it cheesy. If the group wants to enter into a hip culture, it has to be prepared to be judged by those terms; its affected seriousness and stilted pre-planned movement wouldn't stand a chance next to the smooth flow of pop acts.

Muskal's music meandered with little purpose other than to be subservient to the visuals. On top of it all, the projections actually limited Eighth Blackbird's visual impact by focusing it in on the small screen.

Eighth Blackbird may claim darling status with this move to visual delights, but unless it can increase its quality and pick better music, it runs the risk of hurting its primary mission -- bringing audiences new music that we want to hear, not see.