On a recent morning, Greg Hobson tinkered with a wind chime he made from an old bicycle wheel, making sure it correctly played the tones from the movie “Close Encounters of the Third Kind.” Greg certainly knows his tones.

“It’s in a C major pentatonic scale,” he explains.

Interesting things happen when a music-loving engineer retires from a refinery.

At Greg and Pam Hobson’s Sharpe Road farm, there are bees, ball-fetching donkeys and white doves that can be hired for release at weddings. Now, with more time on his hands, Greg also has started producing a bumper crop of down-home style musical instruments, handmade from mostly recycled materials. The couple sells them under the brand Rosario Farm on eBay, at the Anacortes Farmers Market and at The Business.

“All are under $150. Most are around $125,” he said.

At the market earlier this month, visitors stopped to watch as Greg demonstrated a banjo he made from a 1963 Rambler hubcap. He explained that model and year is best because of its rich tone and flat strumming surface.

Another big plus: “It’s satisfyingly funky,” he said.

The Hobsons began making beautiful music together in school.

“We performed at the Anacortes Arts and Crafts Festival back in 1971,” Greg said.

“He played the keyboards and I sang,” Pam said.

Pam’s brother Tim Wittman led their rock group, and the three still perform in the folk group Windsong. Greg later picked up stringed instruments for daughters Tessa and Ana.

“He’d always be playing something when they were toddlers,” Pam said.

Now the whole family performs together.

“We’re a musical family. It’s a hobby that connects us all,” she said.

Pam plays Celtic harp and sings in church. Violinist Ana performs in a quintet and recently got a standing ovation for a solo with Fidalgo Youth Symphony. Tessa plays violin and viola. A couple years ago, the sisters took turns playing the Fiddler in Anacortes Community Theatre’s “Fiddler on the Roof.”

The daughters and their friends watch with amusement as Greg enters his mad-scientist style workshop to create cigar-box banjos, propane tank drums and other assorted instruments. He’s experimenting with a door harp, a Ugandan amadinda xylophone and an assortment of guitars, dobros, music boxes, flutes and whistles.

“There’s a lot of things under development,” he said.

After graduating from Anacortes High School, Hobson earned a degree in mechanical engineering from Washington State University. He initially studied music at Western Washington University and considered a career teaching and performing, but “I talked myself out of it,” he said.

After graduation he went to work at the Texaco refinery, now Shell Puget Sound Refinery, where he was a process control engineer until his retirement last July.

His first handmade instruments were beautifully carved African slit log drums.

“I started making these probably 14 or 15 years ago for family Christmas presents,” he said.

He grew obsessed with trying to tune the drums to a scale, but was thwarted by the nature of the wood and other variations.

“It just didn’t prove feasible. I started looking around for a way to make a tunable instrument,” he said.

Greg discovered Michigan “instrepreneur” Dennis Havlina’s Web site Oddstrument.com, which offers resources about DIY musical instrument projects, construction details and instructions. That’s where he found the idea for propane tank drums, which can be tuned by the length and width of his cuts. He was also inspired by the ability to use found materials.

“I liked finding inexpensive materials. These are all recycled,” he said, pointing at a cluster of brightly painted propane tank drums. “They’re used tanks. They’ve all been sandblasted inside and out.”

He said the drums are fascinating to working men, who come up to him at the Farmers Market wondering how he safely applies torches to gas tanks.

“I get welders coming up and asking, ‘How do you make sure you’re not going to kill yourself?,’” he said.

Greg is particularly careful when cleaning out the valves, and he soaks everything in water and heavy duty detergent for a few days to neutralize the gas.

Shortly before he retired, he built his first few stringed instruments. His first banjo was made using a metal Ghirardelli chocolate box. Soon he was making guitars, banjos, mandolins, dobros and more.

Cigar-box guitars, banjos and kalimbas have been among the more popular items. Like oldtimers on the Mississippi Delta, Greg appreciates the quality of sound the boxes produce. He illustrates the phenomenon by setting a wind-up music box on a cigar box to show how the volume is amplified.

“These resonate really well,” he said. “It’s amazing workmanship that goes into these things.”

Many Web sites are dedicated to the funky instruments, and numerous famous musicians have used them.

“Cigar-box guitars have been around since cigar boxes were invented in the 1840s,” he said.

Greg gets most of his boxes from cigar retailers and wholesalers, such as the Swinomish Smoke Shop, although some vintage boxes come from eBay. His cigar-box instruments all come with microphone jacks, which hook up to amplifiers he makes from cigar boxes.

For the necks, he uses fairly hard wood like oak or mahogany.

“Wood like metal has different stiffness coefficients,” he said.

He prefers recycled or sustainable local wood. Favorite sources include a wood recycler in Bow-Edison and the ReStore in Bellingham. He’s been known to use old flooring.

“I try not to use tropical rain forest wood,” he said.

Greg uses sink drains to channel sound on his instruments. He picks up old hubcaps at yard sales and Shipwreck Day.

He got a good deal on a big box of rusty old wrenches at The Mercantile and created a “Wrench-O-Phone.” To prove it is in tune, he picks out the old Harry Belafonte song “Kingston Town” on the instrument.

Greg said he’s working his way around technical issues such as the need to have a fifth string tuner on the side of a banjo, and has worked out a couple of alternatives. He typically does not add truss rods to his necks, which are often inlayed to make stringed instruments stronger but are prohibitively expensive.

He shows a solution — a metal piece cleverly bolted to the back of a banjo.

“I call it the Hobson Adjustable External Truss Rod,” he said with a laugh. “I should patent it.”

The Hobsons sell up to 18 instruments at a time on eBay in the winter and at the Anacortes Farmers Market in the summer. Pieces have been shipped across the country and to Japan, Spain and England.

“One woman bought a pair of the tank drums for her twin autistic sons. She wrote and said they had a blast with them,” she said.

Pam said they sold 98 pieces in 2008, after founding the business in July.

“I call her the president and the business manager,” he said.

“I’m the shipping department,” she said.

The Hobsons have a Web site, http://www.rosariofarm.com, which links to several YouTube videos of Greg playing a variety of his instruments. But Greg said he prefers the Farmers Market to the Internet.

“I really enjoy that place. You get a lot of good feedback. People are so interested and so interesting,” he said.

Pam, who recently completed a term as president of the Fidalgo Youth Symphony, said Greg’s enthusiasm for experimentation has broadened her world.

“I used to be the one to put the brakes on. He taught me to take the brakes off,” she said.

Now she’s figuring out what she might build herself.

“When I get more time I’m going to make some things too,” she said.

Greg said the chief purpose of making the instruments is not to make money.

“It’s to have fun. I enjoy having the feedback from people. It’s an education too. I’m always learning something new,” he said.