With so much musical hardware on the Perelman Theater stage, is there still room for a Prism Quartet?

That was a valid question last week, and it will be again at 7:30 p.m. Saturday, for the 32-year-old Philadelphia saxophone quartet, which has an appetite for collaborating with ensembles requiring much stage real estate. Last week, they played with the modern percussion ensemble So Percussion. On Saturday, they will perform with a Los Angeles group known simply as Partch, which plays versions of the exotic instruments invented by maverick composer Harry Partch (1901-74).

For this collection of fantastical sound-makers, the Kimmel Center's smaller auditorium has been modified into its deep-stage configuration to make the kind of room usually needed only for opera. Might Prism be subsumed, eclipsed, or otherwise lost?

Surely, the sax quartet sets boundaries. "We never discuss limits, just possibilities," says Matthew Levy, cofounder of the group, executive director, and tenor saxophonist. "How could we not pose the simple question: What would a sax quartet sound like with microtonal Harry Partch instruments?"

For Saturday's concert (repeated on Sunday at the venue Roulette in Brooklyn), composer Ken Ueno added extra tubing to one of the Partch instruments - dubbed a "hookah sax" - for his piece Future Lilacs. It creates deep, almost subterranean sounds with organlike effect on the ensemble, and perhaps an even more visceral impact on the performer. "My whole mouth and head are vibrating," said Prism member Zachary Shemon.

The original set of Partch instruments was once housed at relatively convenient Montclair State University in New Jersey, which is where pop star Paul Simon recorded them as an exotic backdrop for what became his Stranger to Stranger album, released only last week. Now, Prism is working with copies of the originals owned and played by Partch.

The nine instruments coming to Philadelphia - with names such as chromelodeon and cloud-chamber bowls - collectively weigh 2,473 pounds, with transportation costs of approximately $10,000, equal to a healthy performance fee for a star soloist.

"There was sticker shock," admitted Levy. "We have a 16-foot truck with a lift gate - and a very detailed schedule. But the music is breathtaking."

Instruments once considered a curiosity - with the usual 12-pitch octave divided into 43 microtones - are now more of a "gorgeous Pandora's box," said Partch leader John Schneider. "It's as if you spent most of your life in a city and suddenly you're plopped down in the middle of jungle in South America with more colors than you've ever heard before."

"They really have to be experienced live. There's a tonal lushness and natural earthy quality," said composer Ueno. "It's like watching high-def TV. You can get finer colors."

The overall project is called Color Theory, an open-ended concept that invites all manner of alternative sound. In works by Georg Friedrich Haas, the four instruments of the quartet blend into something resembling an electronic pulsation. Then there are collaborations, with groups such as So Percussion and Partch, that explore color with a wide range of instruments, often played in unconventional ways.

"It's kind of too easy," said Princeton composer Steve Mackey. His new piece Blue Notes and Other Clashes was the hit of last Saturday's Kimmel concert. "Color is an important preoccupation with all of my music. The challenge for me was to be more [coloristically] specific, which is why I home on this idea of making 'wrong' notes sound right."

He acknowledges his publisher doesn't love the way Mackey dives into practicality-defying projects with unusual instrumentation that no doubt limits the music's performance opportunities. But having worked with Prism for more than 25 years, he wouldn't miss this for anything.

"When you walk into an orchestral rehearsal for one of your new pieces, you'd better know what everything is going to sound like," he said. "But these musicians meet you more than halfway. They want nothing more than to get inside your head."

Learning to play a hookah sax is a minor challenge in the larger world of the Prism Quartet. The Brooklyn rehearsal space with So Percussion was so cramped players wore earplugs due to the magnitude of sound. (Mackey wasn't offended; he wore them, too.)

Yet another manifestation of color theory is the once-marginalized Partch himself. Truly a maverick figure, he spent some of the 1930s as a hobo and migrant worker, which contributed to his alternative musical viewpoint. Some of his early instruments were said to be constructed from discarded junk. He considered himself primarily a musical thinker who built new instruments out of necessity. Partch later became a respected presence at the University of Illinois, among other places, thanks to his precise interpretation of ancient Greek music theory.

Those who heard the instruments in 1987, when the American Music Theater Festival here staged Partch's Revelation in the Courthouse Park, perhaps didn't really hear them due to the acoustic challenges at the University of the Arts performance space. And with the increased presence of world music on the general landscape in the 21st century, the Partch instruments perhaps no longer sound foreign.

At least to the audience's ears. Composers and performers in this concert are faced with matching traditional scales with Partch's. Much of that, says Levy, involves bending saxophone pitches using jaw pressure and other highly intuitive techniques. Ueno compares blending the two worlds to "speaking multiple languages. It's a polyglot approach . . . more globalist . . . like mixing and matching different words for specific needs."

Levy has a strong sense of mission in creating a saxophone quartet repertoire. Most of Prism's more important new-music commissions - including the ones unveiled this month - are being recorded for release. After all, the sounds are likely to be supremely otherworldly - with the possible exception of, say, a combined saxophone quartet and gamelan. And in Prism circles, that possibility is indeed under discussion.


Color Theory Concert: Prism Quartet and Partch
7:30 p.m. Saturday at the Kimmel Center's Perelman Theater, Broad and Spruce Streets. Tickets: $10-$28. Information: 215-893-1999, kimmelcenter.org.