WHEN A GROUP of Oregon Symphony players got together in 1985 to form Third Angle, devoted to performing new and often challenging contemporary classical work, they were the only game in town.

"We were it," says Ron Blessinger, violinist and Third Angle's artistic director since 2000. "There was one new music ensemble in Portland, and now there are dozens. I think that the audience for new sonic experiences is growing, and people are more eager than ever to hear stuff that isn't pop."

While Blessinger and his rotating cast of players are not alone anymore, Third Angle remains the city's most well-known chamber ensemble. They've been invited to perform in Beijing and Thailand, commissioned pieces from composers living around the globe, and have made deep connections with like-minded organizations.

That is, in part, how Third Angle decided to kick off their 30th anniversary season with the first-ever Oregon performance of Timber, a piece written by Michael Gordon of the New York-based contemporary classical group Bang on a Can.

"We've developed a really good relationship with them," says Blessinger, "and love them as people. When Michael announced this new work, we were eager to hear it and knew we had to program it."

Timber is a hypnotic swirl of percussion, with the six required players slowly morphing from rapid-fire patterns to slower, steadier pulses. Sometimes it is in unison, but just as often the rhythms fall out of phase for a slightly dizzying effect. When it is performed at the Alberta Rose this Friday, Third Angle will be joined by members of Mantra Percussion, the ensemble that premiered the piece in New York.

Musically, it bears some resemblance to percussive efforts by minimalist composer Steve Reich, yet Timber is made unique by Gordon's choice of instrumentation: simple blocks of wood. Each one is played using mallets to bring out its natural pitch, and is amplified using contact microphones, but otherwise the musicians are quite simply banging on two-by-fours.

Where it gets even more interesting is that the composer offers up no requirement about what kind of wood to use or the length or width of the individual pieces. It leaves plenty of room for variation.

"The six pieces have to be graduated in terms of their range, from a high-sounding board to a low-sounding board, and the score is specific about dynamics and rhythm, but nothing else," says Blessinger. "Our players have a lot of options for how they play their wood."