Patrick Costello began losing his hearing as a young child, forcing him to find non-traditional ways to master instruments, including the banjo. He is now a renowned instructor with over 11,000 YouTube subscribers. (Ashleigh Joplin/The Washington Post)

Patrick Costello hadn’t completely lost his hearing, but by third grade, a lot of it was gone, so he wasn’t totally following the school assembly.

A blind woman was telling the elementary school students about the ways she adapted to everyday life. Costello thought she said something about her seeing eye dog and something about how she gets across the street.

Then she took out her guitar. And when she instructed the children to sing along, they all joined in.

“I knew these kids. They were monsters. And she had them in the palm of her hand,” he marveled. “We’re being told that she’s handicapped. But I’m seeing that she is so powerful.”

The boy watched the woman who could not see, making music that he could not hear.

A family photo shows Costello when he was 2 years old, before his family realized he was going deaf. The photo is displayed at his parents' home in Crisfield, Md. (J.M. Eddins Jr./for The Washington Post)

And with tears running down his face, he suddenly knew what he wanted to do with his life.

“I just knew music was the answer.”

Thirty-five years later, Costello, 44, is a full-time musician. Despite deafness, epilepsy and a recent debilitating addiction to painkillers, he has performed and taught the banjo all over the world. From his parents’ home on the isolated tip of Maryland’s Eastern Shore, he creates books and videos for a devoted and growing audience.

When he could not hear, he learned to play the guitar and banjo by feeling the vibrations with his teeth pressed to the instrument. He learned the logic of music, the way notes and chords go best together, so that he could perform concerts without his disability being evident. So that he could speak lovingly about the “beautiful melody” of a folk song he had never experienced in the way his listeners could. So that he could compose his own music.

Costello insists that his feat in becoming a musician is not so different from anyone else’s. Music is physically challenging for every practitioner, he says. “You’re telling one hand to do this, while the other hand does that, while your body does something else.”

It is that spirit — humble, folksy, straightforward — that draws students to his music lessons, which he has offered online since the late 1990s.

He has written seven music books, including guitar and banjo textbooks, a book of gospel songs and a collection of essays on music.

Costello playing a dobro. (J.M. Eddins, Jr./for The Washington Post)

The accounting brains in Costello’s music business is his father, Joseph Patrick Costello II, who goes by Pat while his son, the third Joseph Patrick Costello, goes by Patrick. In Patrick’s videos and writing, Pat is always “Dear Old Dad.”

Dear Old Dad won’t share exactly what their income from music is, but he says that the father-son business has sold 9,000 to 12,000 books and DVDs in the past decade. Their Web site, DailyFrail.com, gets more than 1,000 visitors a day.

But most people who use Patrick Costello’s music lessons don’t pay for them. All his books can be downloaded free, and he has posted hundreds of videos to YouTube, where he has more than 11,000 subscribers and his clips have been viewed more than 4 million times.

Neuros Moonshiner, a Swedish musician who headlines an eponymous heavy metal band, called Costello “the merry God of banjo” in an e-mail to The Washington Post.

Moonshiner learned the banjo by watching Costello’s videos. He plays banjo on his next album, and he asked Costello to provide some voice tracks.

Costello’s fans have paid him tribute in all sorts of ways — by traveling from other continents to his banjo conventions in Cris­field, by writing notes saying his lessons helped them deflect suicidal thoughts, by mailing him instruments.

“Through 600 videos, people really feel like they know me,” he said. “The real Patrick Costello’s never going to match up.”

To one fan, though, he more than measured up to expectations.

A government contractor from Manassas picked up the banjo and soon found Costello’s videos. In 2009, she traveled to Crisfield to attend his convention.

“I saw him and I went, ‘I’m gonna marry this guy,’ ” she said. “Even though there’s the guru banjo person, I saw a genuine, authentic man.”

Amy Costello was right.

Patrick said it was also the perfect time for him to meet Amy. After decades of deafness, he had just had a bone-anchored hearing aid implanted in his head, restoring much of his hearing.

“You know how hard it is to meet people when you can’t hear? I wouldn’t wish it on the worst person in the world,” he said.

After their marriage, he moved out of his parents’ house in Cris­field, where he had lived for more than 20 years. He had held a variety of jobs, including a longtime janitorial job at the local hospital, before making Daily Frail into his full-time job.

In Manassas, he quickly filled Amy’s apartment with music. When a reporter visited last spring, Costello gestured toward a corner where at least seven instruments were leaning against the wall.

The dulcimer, he said, is “one of those instruments designed for nothing more than happiness,” whereas the harp is “designed to make you completely miserable.”

But his life in Manassas was plagued by medical problems. There was the growth in his ear, called a cholesteatoma, caused by the repeated ear infections that had taken away his hearing starting before he was 3 years old. After multiple painful surgeries on his ear, he had more operations — one for a gallbladder problem, then on his shoulder and his neck to fix injuries from a car crash many years earlier.

He said that he had never used alcohol or drugs other than tobacco. The painkillers he was prescribed after his surgeries were addicting.

Eventually, crippled by withdrawal symptoms, he went back to Crisfield, where he said he felt more confidence in the medical care he received and felt he wasn’t a burden on his wife.

Costello has been overcoming his addiction with Suboxone and hopes to stop taking that soon. But he’s not so sure he wants to leave Crisfield.

“My dream is to get the business to a place that I can get my own place and move [Amy] down here,” he said.

At his parents’ house, about a mile from the Chesapeake Bay and more than 100 miles south of the Bay Bridge, the living room is adorned with dozens of quilts sewn by his mother, Trudy. They rest on rocking chairs, hang from walls, tower in multicolored stacks that overflow bookcases.

Costello said as a child he sat at her feet while she sewed.

“When I started losing my hearing, she never acted like it was anything different,” he said. “What kept me from going crazy was what Mom did. She always encouraged me to use whatever I had.”

It was that lesson, he said, that helped him become a musician. He found a guitar in a trash can as a teenager, fixed it up with duct tape, then tried to play. He couldn’t hear the sound. In despair, he slumped. His head rested on the instrument. And suddenly he felt its vibrations.

That was when he realized that in this case, using what he had meant using his teeth.

“I forget sometimes. I get really frustrated,” he said. But then he thinks of his mother’s quilts, painstakingly assembled one square at a time. “Part of being in the arts is being frustrated. You’ve got all these ideas in your head, and you want them all to come out at once.”

Costello has tried to share that message with other disabled musicians. He taught music at a camp in Kansas for children with cerebral palsy and spina bifida. When a blind musician in the Netherlands asked him to create banjo tablature in Braille, he came up with his own system and has since shared it with other blind banjo players.

“This is the magic for our family,” Trudy Costello said proudly. “It’s not the number of days you have or anything else. It’s what are you going to do? How are you going to make somebody happy?”

Her husband plucked the banjo on his lap, picking out the first verse of “The Wreck of the Old 97.” Wordlessly, Patrick joined his father on the guitar. They switched back and forth — one playing a rollicking melody, one adding rhythm, then the other way around — needing no communication but their grinning eyes.

“It’s not magic,” Patrick said with a broad smile. “It’s familiarity.”