Martin Feldman could very well be called “the accidental cantor.”

One night many decades ago, a cantor at a Reform temple in South Orange, N.J., got laryngitis shortly before services were to begin. Feldman, who as a young man sang tenor in a professional quartet, was there to sing that night. The rabbi knew that liturgical pieces were among Feldman’s repertoire and asked whether he could substitute for the sick cantor.

After the service, a congregant approached him and said, “Cantor, you have a beautiful voice.” That, said Feldman, “put the bug in my head.”

That story is now well known among his congregants at Congregation Sherith Israel. And now, after 43 years of serving one of San Francisco’s largest congregations, Feldman is retiring. He’ll leave in May, a month shy of his 75th birthday. Cantor Rita Glassman, formerly of Congregation Beth Sholom, will take Feldman’s place at the Reform synagogue in July.

Feldman’s farewell will be 7:30 p.m. Friday at a special Shabbat service (in memory of Gusti and Walter Mollerich) and concert. He will be joined by other musicians.

Growing up in a musical family in Newark, N.J., “everyone always told me I had a beautiful voice and should do something with it,” Feldman said. His sister played piano, his brother played mandolin, and Feldman sang. Though he continued to perform while in high school, when he graduated he didn’t consider making music his career. “Physically, I wasn’t a budding Broadway artist,” he said. “I wasn’t an Eddie Fisher. I didn’t know what direction to follow.”

He began studying to become a teacher, but that fateful remark by the congregant caused him to rethink his path.

Soon after, he entered Hebrew Union College’s School of Sacred Music. Upon being invested, he worked for two years in Tarrytown, N.Y.

Though Feldman had never been to California, when he heard about the opening at Sherith Israel, he sent off a tape. Soon he was driving across the country to take the job and work alongside Rabbi Morris Goldstein. It was 1960, and Feldman was 32.

He soon met his future wife, Nancy, on the tennis court. Now they have two grown children and six grandchildren.

Being in one place for so long, he has witnessed countless lifecycle events. “Being able to interact with families this way, teaching a child for his bar mitzvah, through his marriage, baby naming, and a death, you only can get this when you stay umpteen years,” he said.

By his own estimation, he has helped more than 1,700 children prepare for their b’nai mitzvah, as well as several hundred adults. He began the adult program 28 years ago.

The adult b’nai mitzvah services are “among the most moving I have attended,” said Rabbi Martin Weiner, who has worked alongside Feldman for the past 31 years. “Each year, people are hesitant about standing up in front of all those people,” said Weiner. “I know that the cantor will lovingly encourage and cajole each of his students to share fully in the b’nai mitzvah service. Through laughter and tears of joy on the day of the service, I know how much this experience has meant to each of the b’nai mitzvah.”

At the other end of the spectrum, through his association with Sinai Memorial Chapel, he has also participated in his share of funerals.

“In Jewish lore, we speak of the ‘Sweet Singer of Zion,’ said Weiner. “Cantor Martin Feldman has been that sweet singer for each of us at Sherith Israel and for our community.”

Feldman has seen numerous changes in the cantorate during his long tenure. Of course, when he entered HUC, there were no women in his class. Today, the majority of those studying for the cantorate are women. But perhaps the greatest change he has seen has been the introduction of the guitar.

As one would expect, Feldman can cite many highlights over the years. One was his performing as the principle soloist of Ernest Bloch’s “Avodat Hakodesh,” or “Sacred Service,” which he did with a 30-piece orchestra on the occasion of his 30th anniversary with Sherith Israel. Working with his colleague Rodney Gehrke,”one of the country’s finest choir directors and organists, a marvel,” has been another. Once he retires, Feldman plans to play more tennis, spend more time with his grandchildren and occasionally serve as a cantor on a cruise. While he knows it’s his time to step down, he is wistful about what he will miss.

“I’m going to miss singing in that magnificent sanctuary. The acoustics in that synagogue are beautiful, especially when the lights are dim and there’s a full house for Rosh Hashanah and Yom Kippur.”

Feldman said he got teary at High Holy Days this year, knowing they would be his last as cantor. “The sanctuary has this dome, and when the choir sings from the dome, you can’t duplicate a sound like that,” he said. “It’s like 100 angels singing from heaven.”

Said Weiner: “Each year as I stand with the cantor as he chants ‘Avinu Malkeinu,’ I am near to tears,” said Weiner. “I always whisper to him how beautiful it is.”