"H ow often do you go to a string quartet concert where people are tapping their feet?"

It's not just a rhetorical question from Mark Summer, cellist and founding member of the Turtle Island Quartet. Over its 25-year history, the Bay Area ensemble has become known for pushing the boundaries of what can be done with 16 strings, and they stretch in even newer directions on their latest CD, Have You Ever Been . . . ?

Eight of the disc's dozen tracks are replications of songs recorded by Jimi Hendrix, mostly from his landmark Electric Ladyland LP, each thoroughly deconstructed and retooled for TIQ's markedly different instrumentation.

"You'll see the quartet operating like a band, creating all the parts," Summer explains, "really trying to harness the energy that [the Jimi Hendrix Experience] was able to create, the focused power of what starts out as the blues and goes someplace quite amazing."

How do they do it?

"What I do is create the 'bass and drums,' hitting the instrument on the fingerboard and playing it like a bass, part of the time, and part of the time playing it with my bow," he elaborates. At other times, rhythmic roles are spread around among all four players. The violins and viola "do something called a chop, which is from bluegrass, like an imitation of a snare drum sound," often played on mandolins as well as fiddles. "You use everything you've got to create rhythm."

But for one track, Summer is entirely on his own, performing "Little Wing" as a solo showcase for his instrument. "I had to use it in many different ways, so the cello is imitating the sound of the electric guitar, the iconic opening when Jimi slides down . . ." He approximates a vocal demonstration. "But I'm also playing pizzicato parts imitating the sound of the bass, and then striking the instrument on the fingerboard to create a drum sound. And it's not easy; it's very physically demanding."

This is a long way from Summer's conservatory training, but a precise fit with the intent of the TIQ, which first came together in 1985. "The idea was to have four string players who were equally versed in the art of improvising but also classical and bluegrass, jazz, be-bop," Summer says. Moreover, they almost exclusively play original compositions or arrangements, mostly scored by co-founder David Balakrishnan.

"We're coming from the chamber music tradition and we're paying homage to it, and then we're taking it into the 21st century," Summer summarizes. "We're very aware that we're not playing electric guitar, bass and drums; we're playing stringed instruments," he concludes. "This is a quartet that Joseph Haydn would recognize."

The Turtle Island String Quartet perform Friday, March 18, at the Marin Center. 10 Avenue of the Flags, San Rafael. 8pm. $25-$35. 415.499.6800.

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