BRUNSWICK – With his eyes closed and his violin clutched to his chest, Lewis Kaplan listened Monday morning to 15-year-old Muyun Tang as she played a selection from Johann Sebastian Bach on her own violin.

But he wasn’t just listening. He swayed. He blurted out “that’s great” or “much better.” At times he sang what the tune should sound like, or he played it himself.

Several times during a half-hour lesson with Muyun, he dispensed his musical philosophy.

“Bach was a religious man. He believed all music was at the service of God,” said Kaplan, 80, during a break in Muyun’s playing. “Why is Bach arguably the greatest composer? It’s his use of harmony. Try to imagine (the music) as real voices.”

During the 50 years since he helped found the Bowdoin International Music Festival in Brunswick, Kaplan has been at the center of the event’s growth from a small summer workshop for a handful of musicians to an internationally known festival that attracts 250 students and 60-plus faculty from around the world. Festival faculty and students stage 80 or more concerts each year. Tuition for students for six weeks is $6,100, including room and board.

This year’s festival concluded Saturday, marking the end of Kaplan’s 50-year tenure as the festival’s only artistic director. He intends to continue as an instructor with the festival and will travel with a group of festival faculty to China in the fall to help start a classical music event there. The festival will now have artistic co-directors, brothers Phillip and David Ying, who are both faculty members.

While Kaplan’s vision and passion for music education have definitely shaped the Bowdoin International Music Festival, people connected with the festival say his ability to inspire others is probably the greatest contributing factor to his success.

“Every teacher has something you can learn from them. With Mr. Kaplan it’s his inspiration. You don’t teach the details to a musician, you try to inspire them,” said Muyun, a native of China who is studying at the Juilliard School in New York City. “I don’t think of him as the one who controls the festival. I think of him as doing his best to make it better, to inspire others to make it better.”

But inspiration doesn’t keep a six-week-long festival with a budget of $1.5 million running smoothly. Kaplan is also pragmatic and the kind of visionary who is rooted in reality.

“He’s a visionary and an agent of change, but not a dreamer of things that could never happen,” said Maryan Chapin of Georgetown, a festival board member and former chairperson. “He’s very unusual for an artistic director in that he understands money. If we want to give scholarships, we have to fund them.”

Phillip Ying thinks that Kaplan’s legacy lies in the standards he set for the festival, in terms of the quality of the musicians and the quality of the experience for students.

“He’s very modest and will tell you there was no vision for the festival, that things just developed. He didn’t have a vision for X number of concerts and X number of students, but he’s always had this uncompromising view of musical standards,” Ying said. “He has an equal passion for nurturing young musicians.”

BORN WITH A PASSION

Kaplan has no easy explanation for his passion for music. His father was a lawyer and politician in Passaic, New Jersey, and his mother was a homemaker. Neither was particularly musical. But when Kaplan was 4 years old he heard a violin “someplace” and begged his mother to get him one.

His mother wanted to get him a toy violin to play with. But his grandmother, who was from Austria, suggested he should have a real violin.

He took lessons, but said “the guidance was not good” in his early years as a violinist.

Then, when he was a teenager, he had his own Bowdoin International Music Festival moment. He began studying with renowned violin teacher Ivan Galamian and become serious about pursuing a career in music. Later, when Kaplan was an adult and had already spent many years as artistic director at the Bowdoin festival, Galamian asked him to come to work at his summer program, Meadowmount School of Music in Westport, New York.

Galamian wanted Kaplan to be “one of his successors,” Kaplan said. But Kaplan decided to keep spending summers in Brunswick.

“We are all composed of what we have taken and what we have rejected,” said Kaplan, thinking about that possible turning point in his career.

After graduating from Juilliard, Kaplan founded the Aeolian Chamber Players, a mixed timbre ensemble and a model for hundreds of other ensembles. He began teaching at Juilliard, which he still does, in 1964.

Kaplan first came to Bowdoin College in the early ’60s to visit his brother, who was a student there. That’s how he met and became friendly with Robert Beckwith, chair of the college’s music department.

Kaplan said he got a call from Beckwith in May 1964, asking if he could bring his Aeolian Chamber Players to Bowdoin that summer to do a concert.

Beckwith also asked, casually, if Kaplan could bring with him some ideas about starting a summer music school on the Bowdoin campus as well.

“Uh, yes,” Kaplan remembers saying.

INSTILLING IDEA OF SUCCESS

Kaplan and Beckwith started the festival together, and ran it for many years in conjunction with Bowdoin College. But in 1997 the festival became an independent nonprofit organization, renting space from the college.

The festival makes the campus a lively place in summer, with students carrying instruments from building to building. It also fills the Brunswick area with music. Admission to concerts and other events ranges in price from free to about $40.

Over the years, Kaplan was able to attract the best teachers and performers to the festival. In 1966, Arthur Fiedler of the Boston Pops was a guest conductor. More recently, the festival’s roster of performers has included Ray Chen, a violinist who has achieved rock star status among classical music fans and musicians.

Kaplan says he’s excited to step down as director and devote more energy to other things, mostly to teaching and to his students. He’s learned that what works best, for him anyway, is to criticize a student’s performance “even deeply,” while still being able to convince the student he or she can succeed. It’s a thin line to walk, Kaplan admits, but after all these years he feels he knows how to do it. And he knows it works.

“It comes from my own sensitivity, my own experience,” said Kaplan. “There are some advantages to being 80.”