There was a moment on that 2006 trip to Costa Rica that Paula Fan questioned her sanity.

Steven Moeckel had roped her into a lot of crazy adventures, but this tipped the scales: ziplining across a city park.

"I was going really fast the wrong way around and (a worker) caught me and flipped me (over)," the longtime Tucson Symphony Orchestra principal pianist recalled. "I thought to myself what are we doing? But what the hell."

"I've always wanted to do that. It was phenomenal fun," chimed in Moeckel, the TSO's former concertmaster. "We were both a bit concerned at the start, but that was a great day."

The pair's 10-year friendship and musical collaboration has long been based on wacky adventures, from spending a week in the frozen tundra of Helsinki, Finland, to recording an entire CD in a nonstop nine-hour session in London.

But next Sunday, the pair will do what is perhaps their wildest adventure to date - a 12-hour marathon concert that will survey their friendship and their musical partnership.

"I've never done anything like this before and I've never heard of anyone doing anything like this," said Moeckel, 35, who came up with the marathon as a fundraiser for Open Inn, an organization that helps at-risk and homeless teens. "That's what we want, for people to be inspired."

Fan and Moeckel's friendship started as an arranged marriage of sorts. The TSO put them together in 2003 for a recital as part of Moeckel's concertmaster role.

They met in the Tucson Symphony Center parking lot not long after Moeckel arrived in Tucson. They chatted for a moment, "then we said let's eat," Fan, 60, recalled.

"This has been a big part of our relationship; both of us are wondering where our next meal is coming from," she said with a laugh.

When they returned to the symphony center that day to run through their recital piece, "it went click," Fan said.

"It's chemistry, and we realized there was this chemistry and you never know when it's going to show up. I had it when I played with my husband (the late Tucson clarinetist John Denman) and with a few other players," Fan said.

"We discovered immediately that we got along very well on a professional level and a personal level," added Moeckel, who left Tucson in 2008 to become concertmaster with the Phoenix Symphony.

The pair went on to record three CDs together in London and perform as Duo Amabile around the world, including in Helsinki, when Moeckel competed in the prestigious Sibelius International Violin Competition in 2005. Moeckel, accompanied by Fan, made it to the contest's semifinals.

"It was cold and it was insane. Neither of us spoke Finnish, but we found ways to make it work," Fan said.

A few months ago, when the pair considered how to mark their 10th anniversary, the thought of a quiet meal came to both of them. But where's the challenge in that? Moeckel joked.

"It's absolute insanity," he said of playing the 12-hour concert, which will be broken into two-hour segments. "Here's the thing: I could only do it with someone I've played 10 years with. We have played so much together, we've done so much repertoire … that we barely have to rehearse any more because we know each other so well. it's been a great friendship and a great partnership."

Read about the marathon concert in Thursday's Caliente.

If you go

• What: "Playing for the Future," a marathon concert to benefit Open Inn.

• Featuring: Steven Moeckel and Paula Fan with friends including musicians from the Tucson Symphony Orchestra, Phoenix Symphony and several high school orchestras.

• When: 10 a.m. to 10 p.m. next Sunday. Moeckel and Fan will perform in every segment.

• Where: Tucson Scottish Rite Cathedral, 160 S. Scott Ave.

• Tickets: $50 for an all-day pass, $10 per two-hour segment by calling 301-7201.

• Silent auction: From 3 to 7 p.m., you can bid on items including original Japanese artwork and a signed Salvador Dali print.

Contact Cathalena E. Burch at or 573-4642.