The last time Michael Learned and Richard Thomas acted together 30 years ago, they played mother and son.
On Sunday, the pair will play love interests of sorts in Chamber Music Plus' "Confidentially, Chaikovski."
"It's kind of like this weird kind of foreplay without the act itself," Thomas said in a phone interview from New York last week. "It's cool. And I think it definitely has a sexual component, even though it's obviously not overt or never consummated clearly because he had a completely different orientation."
Thomas will read the role of Russian composer Chaikovski - more commonly spelled Tchaikovsky - opposite Learned's Nadejda von Meck, Chaikovski's longtime patron and admirer. The two carried on a 13-year affair by letters, although they never met.
Chamber Music Plus cellist and playwright Harry Clark based the piece on the more than 1,200 letters von Meck and Chaikovski exchanged between 1877 and 1890. They had agreed never to meet.
"It's an affair of the heart between the two of them, and an aesthetic love affair," said Thomas, 61. "It was a love of soul mates, and those are always interesting because they run a parallel track of people's actual marriages and affairs."
The performance reunites Learned and Thomas, who starred for nine seasons in the CBS series "The Waltons" in the 1970s, for the first time since the show ended. Aside from a few "Waltons" reunion movies, they have not acted together since, and they've never done live theater together.
"And that was really the great attraction for me, was to be able to get onstage with Michael, because we both do a lot of theater and we both came from the theater before we did 'The Waltons,' " said Thomas, who is making his Tucson stage debut. Learned has done two other Chamber Music Plus productions. "This will be a special treat to be together."
Thomas acknowledges that people who think of him as John-Boy Walton and Learned as Ma will probably find it hard to imagine the two in these roles.
"I'm not trying to get into an incestuous thing here, but you know we're actors. We can play all kinds of things vis-à-vis each other," said Thomas, who has a role in the new FX series "The Americans" set to debut Jan. 30.
"She's why I'm doing it. I like the subject matter; I like doing concert pieces. But Michael was the bait for me, for sure," added Thomas, the son of professional ballet dancers who grew up surrounded by classical music and dance. "She's a wonderful actress and she's a real theater animal. It's wonderful when you get a chance to see her onstage.
"I'm really looking forward to it. When actors get together to do something once like this, there tends to be a lot of electricity because they haven't gotten comfortable with it yet. So it should be very alive. ... This is a very compelling piece of material and very dramatic."
If you go
•What: "Confidentially, Chaikovski."
• Featuring: Michael Learned and Richard Thomas.
• When: 3 p.m. Sunday.
•Where: Berger Performing Arts Center, 1200 W. Speedway.
• Tickets: $40, $15 for students at chambermusicplus.org
• Details: Call 400-5439.