The idea started on a golf course.
"You talk a lot when you're playing golf," violinist Nathan Cole says.
Cole was seriously dating violinist Akiko Tarumoto. His golfing buddy Burchard Tang, a violist, was cruising toward the altar with cellist Priscilla Lee.
Cole says, "We were remarking that if we got married, we'd be two married couples that are a string quartet, and wouldn't it be fun if there was some summer festival where we could be the string quartet.
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"It was only a year later that we had the chance to do that, and then it was just a matter of bringing in Alessio, who I had played with at the Mimir Festival in Fort Worth (Texas). It was the easiest group that I ever put together."
Pianist Alessio Bax says, "They tried really hard not to make me feel like a fifth wheel."
This musical union of unions enters its fourth year this week with the 2010 Chamber Music Festival of Lexington. The festival's core quintet now has a late August week blocked off on its calendars for music and, they hope, quality down time together.
"That first year, it was a lot of work and not enough play," Lee says. "We are all such good friends, we wanted to hang out and talk and eat, and I remember getting stressed out because we had to rehearse these pieces and get ready to perform."
Tarumoto says, "Now I think we're getting more comfortable and finding a balance between fun and work."
Helping with that formula this year is clarinetist Alexander Fiterstein, who will play on several pieces this weekend.
Fiterstein said he had not been told that the event would be in a horse-auction pavilion. That takes the other musicians back to their first time at the festival, which has always been at the sales hall at Fasig-Tipton Thoroughbred Auction Co. on Newtown Pike.
"Some of us thought it would be more rustic, like a barn, and who knows what the sound will be?" Cole says.
Fiterstein, on his second day of rehearsals, says, "It's very nice."
The festival's audience has grown in size and, particularly nice for artistic director Cole and the musicians, its openness to a variety of works. For the third year, the festival has commissioned a new piece that will have its world premiere at the festival: Roger Zare's Geometries. Overall, Cole and the musicians say about half this year's lineup probably would not show up at most chamber festivals.
A prime example is Friday's second-half piece, Olivier Messiaen's Quartet for the End of Time.
"It's not something I would put on the car stereo or at home to listen to," Cole says. "Being in a concert hall with other people and the performers and letting it unfold is the way to experience it, and that's why it's important to do it live."
Cole likens listening to a recording of the quartet to seeing the science-fiction classic 2001: A Space Odyssey on a small TV screen.
The quintet's growth as a group over the years does raise the question of whether they may become a more permanent act, recording or playing elsewhere.
Noting that they have unedited concert recordings from the previous festivals, which are available for sale at the event, Cole says, "It may be that if we have more time in coming years, we can do a second take without an audience."
As for additional performances, he says, "It's all a matter of scheduling. It takes great effort to set aside this week, and I'm grateful these guys continue to do it. So to get additional days and weeks would be that much more difficult.
"And to do that might lessen how special this is. ... This isn't a traveling show. You have to come here, to Fasig-Tipton, to hear it."