It was supposed to be a cheery holiday performance in front of the large Christmas tree at the Metropolitan Museum of Art, but the music school ensemble seemed to be singing for its survival.

The school, which has served blind and visually impaired musicians in Manhattan since 1913, finds its existence imperiled by its own parent group — a charitable organization with a mission to help the blind.

Singers were led into place by volunteers or guide dogs, but before the music started, the school’s executive director, Dr. Leslie Jones, told the crowd inside the museum’s Medieval Sculpture Hall that the school would be “separating” at the end of the month from its longtime parent entity, Lighthouse Guild International.

This was a cordial take on the situation.

The Lighthouse Guild sent a letter to students in June — in large print, for the visually impaired — notifying them that the 105-year-old school would no longer be part of the Guild’s future and that it must leave the Guild’s building on West 64th Street.

“This decision was difficult because the school has been a part of the fabric of Lighthouse Guild for over 100 years,” Dr. Alan Morse, president of the Guild, wrote in the letter.

Jillian Raquet, 24, who sings in the vocal ensemble and volunteers at the school as a music teacher on Saturdays, recalled getting the letter over the summer. “To find out in some dry letter that we have to look for a new home, it just seemed like, ‘Oh, we don’t really care about you,’” Ms. Raquet said.

Faced with an order to vacate by the end of December, school officials will spend Christmas week packing up 12 grand pianos, its estimable Braille music library and other items, presumably to go into storage.

Ms. Jones declined to comment on the situation, explaining that she did not want to jeopardize the school’s separation arrangements with the Guild. 

She referred requests for comment to the Guild; a Guild spokeswoman said its officials would not comment.

Ms. Raquet provided The Times a copy of Dr. Morse’s letter, which said that the school’s leaders must make organizational changes to “direct our resources to support and serve the largest number of people who are living with or potentially facing vision loss.”

School volunteers and students said the school, officially known as the Filomen M. D’Agostino Greenberg Music School, was scrambling to find temporary space in Manhattan — a daunting challenge, given its limited budget and Manhattan’s high rents — by late January to avoid canceling the spring semester.

Ms. Jones, they said, was scrambling to incorporate the school as a nonprofit in order to organize its own finances and raise funds as well as transfer its endowments and funding streams out of the Guild’s control. The school’s revenue has come from its modest tuition, grants and private fund-raising, as well as funding from the Guild, which also provided space for the school.

“She’s been trying to fight for the future of the school and the survival of the school,” said David Malkin, a lawyer in Manhattan, who helps the school with its endowment.

“What’s going to happen for them is uncertain,” he said of the school. “They’re hoping they’ll find a new home and sustaining support to continue their mission.”

The school has been an unsung staple of New York City arts circles for decades, including 20 years of performances at the Metropolitan Museum of Art and holiday recitals at Midtown Manhattan office buildings.

The blind teenage jazz prodigy Matthew Whitaker is a student there and accomplished alumni include the blind musician José Feliciano, who is currently traveling in Vienna but sent a statement recalling that the school helped him learn music transcription and other skills.

Mr. Feliciano called the Guild’s decision to no longer house the school “callous.”

“Perhaps they don’t care anymore,” he said. “When you consider the school’s benefits and how important and meaningful it is to so many people, it’s just very sad.”

The school serves 120 students, children and adults of varying musical levels. All students attend part time, for lessons, classes and other services, including Braille music transcription.

In addition to several performance groups, the school has an archive of roughly 25,000 Braille and large-print musical scores that it said is second in size only to the collection held by the Library of Congress.

Losing their home has been particularly upsetting for students, some of whom spoke of their disappointment in the Guild, which has long promoted itself as a beacon of hope and an advocate for the blind.

“The school has been such an empowering place and it’s just so painful to see these students being sent a message that blind education doesn’t matter, and that the school is not worth keeping open and they have no say in any of it,” said Leona Godin, a former student.

For more than a century the school was part of Lighthouse International, which in 2013 merged with Jewish Guild Healthcare to form the Lighthouse Guild.

The Guild has also closed the Harriet and Robert Heilbrunn School for students who are blind and have other severe disabilities. Its 33 workers were laid off this month and its 53 students were placed in other schools.

The music school is named after its main benefactor, Filomen D’Agostino Greenberg, a self-taught stock trader who died in 2000 when she was 101.

Mr. Malkin is the director of the Filomen M. D’Agostino Foundation, which donates $100,000 a year to the school, and had served on the guild’s board of directors. But he said he resigned from the board because he was so disturbed by its decision.

Regarding the students, he said, “They are at risk for so many other things, and to lose this resource and opportunity puts them even greater at risk.”

After the holiday concert on Wednesday, one student, Daniel Gillen, 24, tucked away his Braille choral music and picked up his long white cane. He said he was hopeful that the school would find at least interim space.

“We’re not going to be left on the sidelines,” he said.