The story hit just the right note with those who heard it. But whose young voice was it that touched the hearts of both orchestra and audience alike at a concert of the Handel and Hayden Society at Symphony Hall in Boston Sunday?

Well, he’s been found. And his name is Ronan Mattin. He’s 9 years old and his story is remarkable.

Mattin was attending the concert Sunday with his grandfather, Stephen Mattin, both of Kensington, New Hampshire, when the orchestra played Mozart’s “Masonic Funeral Music” as part of the program. As the final solemn and harmonic note ended and silence fell upon the hall, a young voice echoed a stunned, “Wow!”

There was a pause. The audience laughed and then burst into applause.

“It was one of the most wonderful moments I’ve experienced in the concert hall,” David Snead, president and CEO of the Handel and Haydn Society, wrote in an email.

But the orchestra didn’t know who the child was. Snead appealed to the public. If the parents would come forward, the organization wanted to give the boy an opportunity to meet conductor Harry Christophers and get a copy of the recording.

Thursday, the orchestra learned of Mattin’s identity after Stephen Mattin’s sister-in-law learned of the search. Mattin, his grandfather tells WGBH, is on the autistic spectrum. He’s primarily non-verbal.

“I can count on one hand the number of times that [he’s] spontaneously ever come out with some expression of how he’s feeling,” Mattin told WGBH.

Stephen Mattin said he took his grandson to a concert a few months ago and that his grandson loved it. But Sunday’s concert, which was recorded at Symphony Hall to be aired on Boston classical WCRB later this year, drew an audible reaction from Ronan.

“I was there and [it] was an extraordinary moment,” tweeted Marco A. Torres. “The kid’s ‘Wow’ was the best recognition for Mozart’s music and this wonderful orchestra.”

“Lori and I were there,” tweeted Shane C. Woodbury. “I remember that moment, everyone laughed. It was so spontaneous and sincere.”

WGBH Assistant Director of Media Relations Sam Brewer says the Handel and Haydn Society has connected with the family to arrange for Ronan to speak with Christophers.

“Masonic Funeral Music” was composed by Wolfgang Amadeus Mozart in 1785. Mozart was a member of the Freemasons.

Boston’s Handel and Haydn Society, known as H+H, was founded not too long afterward. Founded in 1815, it is the third oldest musical organization in the U.S.