Roy Sakuma credits the 'ukulele with helping pull him out of a family history of mental illness and into a lifetime of teaching and inspiring others through the small stringed instrument.

At 63, Sakuma has been teaching 'ukulele for more than four decades, to everyone from 5-year-old students to grandparents in their 70s.

His business has grown to four studios on O'ahu: in Kaimukī, 'Aiea, Kāne'ohe and Mililani. He has done it all with the help of his wife, Kathy — a business partner, constant companion and best friend through 34 years of marriage.

"We complement each other well. That really helps," Kathy said.

"She is my soulmate," Roy adds.

During his career, he saw a growth in respect for and interest in the 'ukulele, from a novelty instrument or hula accompaniment into its own with a broad repertoire across musical genres.

"When I was first learning the 'ukulele, most people thought of it as a toy," he said.

Now the instrument has gained popularity across the world. And this year, the 'Ukulele Festival he founded will celebrate its 40th year and include former student Jake Shimabukuro — who took lessons for seven years and is an international star.

But Roy and Kathy, 56, remember the early years. "Tiny Tim didn't do much to help," she said, commenting on the off-key singer who accompanied himself in the 1960s on an 'ukulele as a kind of running gag.

The walls of the 'Aiea studio show an 'ukulele hall of fame, along with class after class of strumming students. "I've never really counted," Roy said. "I just want to go out there and teach."

"It's not just about 'ukulele, it's about teaching them values and respect," he said.

And Kathy adds, "I still feel fortunate that we can do something that every day brings joy."

The classes grew slowly at first in the 1970s and 1980s. "In the past five years, there's been a resurgence."

The Kaimukī and 'Aiea locations are open seven days a week. It's five days at Mililani and four at Kāne'ohe.

"Roy and I don't have our own children," Kathy said, so the students, especially those who grew up to be instructors, became their extended family.

The studio gallery includes a photo of Israel Kamakawiwo'ole playing the international hit "What a Wonderful World," backed up by children. (No, the Sakumas don't have the video but figure some parents who recorded their children in 1994 may still have a copy.)

The studios focus on small classes of five or fewer, half an hour each. Both Roy and Kathy clearly love the instrument and the chance to teach.

They are proud to say they've taught three generations of some families.

In 2008, they won a Hawai'i Small Business Administration award for family-owned business.

In January, Roy underwent open-heart surgery and is striving to take things a little easier. But that's not that easy for a man who seems to be perpetually ready for the next inspiration.

Roy remembers trying to learn how to play three times and failing each time — at age 10, 12 and 14. Then in 1963, he heard Herb "Ohta-san" Ohta's pop hit "Sushi" and decided he'd try to learn from the performer himself. He signed up at age 16 and took to it immediately, practicing hours each day.

He learned to play Beatles songs, pop and classical music, as well as Hawaiian. "This little instrument has a lot more than our beloved chalang-a-lang style," he said, tapping one fondly.

Sakuma said 'ukulele master Ohta-san also opened the door to teaching for him shortly before he turned 20, when he talked him into serving as a substitute teacher for his classes.

He thinks back to walking into that first class of 20 adults. "I was scared," he said, until he started playing and knew he'd found his place in life.

"I owe him a lot," Roy says. "He gave me the window to start teaching."

Throughout his early career, Roy still worked as a parks keeper or recreation specialist at Kapi'olani Park, and that's how the 'Ukulele Festival got started there.

Roy gives credit to the 'ukulele for more than just a career. "I grew up totally, totally dysfunctional," he said, in a family plagued by paranoid schizophrenia.

He sat down to play when he was 20 or 21 at probably the loneliest time in his life — and the short but powerful "I Am What I Am" song came to him. "That whole song just poured out of me."

He still plays it at frequent appearances at local schools and still gets heartfelt notes of thanks. "It's telling them just believe in who you are," he says.

And Sakuma's low-key warmth has helped him spread the word.

Sakuma tells of walking around the track at the University of Hawai'i and striking up a conversation with two men sprawled on the grass after working out. They started laughing when he asked if they played football. One said he played music, so after they talked story a little, Roy went to his car to get a CD to give the men, who were on vacation.

Roy got home and told Kathy he had invited his new acquaintances to a dinner cruise that night and casually mentioned that one was named James Ingram. After Kathy stopped asking Roy why he didn't know who Grammy-award-winning singer James Ingram was, she pointed out that he was in Hawai'i to play at a concert.

Once Roy got over being embarrassed about not recognizing the well-known singer, he went on the cruise and they have remained friends ever since.

Ingram has performed at five of the festivals and even co-wrote a theme song for the festival in 2004 called "Come and Join Us."

"It's the most unintimidating instrument," Kathy said of the 'ukulele. "Anybody can pick it up. And not know anything about 'ukulele, just pick a chord and strum, and you're going to feel such joy."