The Portland String Quartet begins its 50th season this week, bidding farewell to one member and welcoming another. Andrew Mark, a cello professor at the Boston Conservatory of Music, will perform his first concert with the quartet on Wednesday as part of the Maine Festival of American Music at the Sabbathday Lake Shaker Village in New Gloucester. On Saturday, the cellist he is replacing, Patrick Owen, will play his final concert with the quartet at the Shaker festival.

For most of its 50 years, the quartet had the same membership, but the retirement of founding members Steve Kecskemethy and Paul Ross necessitated changes. Violinist Dean Stein of Harpswell replaced Kecskemethy in 2013, and Owen replaced Ross in 2015. Owen, who lives in Boston, is leaving the quartet to take a faculty teaching position at the Interlochen Center for the Arts in Michigan, which announced his appointment on Wednesday.

“For so many years, it was the original four,” said founding violist Julia Adams. “For many people, including ourselves, it seemed awfully traumatic to have any change at all, but it is of course natural to have these changes. We were just quite unusual to have a record-breaking 44 years with same four founding members.”

In 2013, Chamber Music America conferred its CMAcclaim Award on the quartet in recognition of the quartet’s longevity and contributions to the cultural well-being of Portland and all of Maine. The award noted the group’s consistent membership, which is said to have been unprecedented among string quartets.

Change has been good for the quartet, said the other founding member, violinist Ronald Lantz. “Each new addition to the quartet brings a different personality, a different outlook on the music and different ideas that we incorporate and grow with,” he said. “It’s a matter of growth for the originals. The quartet can only gain from the new ideas and personalities and approaches to chamber music that we have come in contact with in recent years.”

Mark is a familiar musician to music fans in Maine and across New England. He performed as a guest of the Portland String Quartet after Ross retired, and appeared with Stein in VentiCordi, a winds-and-strings ensemble. He performs regularly with the Boston Pops Esplanade Orchestra and has served as an extra with the Boston Symphony Orchestra and the Boston Pops.

“Andrew is a welcome addition to the quartet,” Stein said. “When Patrick let us know about his appointment to Interlochen, Andrew was the first person he recommended we speak to. Our music making will continue as strongly as it has in the past.”

The 50th anniversary season will be one of celebration for the quartet. In addition to the season-opening concerts next week at the Shaker Village, the quartet will travel to Europe in August to perform a concert of American music in Budapest with a Hungarian choir, and then perform on a river cruise from Budapest. In December, it will perform a free concert at the Mechanics Hall in Portland. The Portland concert on Dec. 21, Adams said, is a gift for the community. “We felt we should have a gift for the city of Portland. We have carried the name Portland around the world, and the city has been very good to us all these years, making it possible for us to be in Portland and have a wonderful chamber music presence throughout the state,” she said.

At Wednesday’s concert, which begins at 7 p.m., the quartet will perform Johann Sebastian Bach’s “The Art of the Fugue.” On Saturday, it will perform “Negro Folksongs in Counterpoint” by Florence Price, an African-American composer, followed by Charles Ives’ String Quartet No. 1 and Johannes Brahms’ Quartet No. 3 Op. 67.

Difficult though they are, the changes in personnel have been good for the quartet, Adams said. “We are just thriving with the new voices and new literature and eye to the future,” she said.

Staff Writer Bob Keyes can be contacted at 791-6457 or at:

bkeyes@pressherald.com

Twitter: pphbkeyes