On Saturday morning, Farah, her sister and their parents sat in their Manhattan home talking about an congratulatory e-mail from Jon Deak, a Philharmonic double bass player who runs the orchestra's teaching program for child composers.
Her little piece, "Serenity Unleashed," was "a big hit" in Pyongyang, he wrote.
"I was just, like ... I was amazed!" Farah said. "I never thought something like this would happen. It was awesome."
The orchestra returned to New York on Thursday from the rare visit to North Korea, which is locked in frosty negotiations with the United States over its nuclear weapons program. It was the biggest American delegation to visit the communist country since the Korean War.
Farah's music almost didn't get played, says Deak, who waited to see whether Korean authorities would allow the child's piece to be added to a long-planned performance in a packed hall.
"It was a wild-card thing," said Deak, who called the piece, written by the daughter of an NYPD traffic enforcement agent, "a tiny gem."
Farah had originally written it for the entire Philharmonic two years ago, and it was played at one of the orchestra's Young People's Concerts at Lincoln Center. But she scaled down the work for a smaller group of musicians - clarinet, violin, cello and double bass, including the Philharmonic's top violinist, concertmaster Glenn Dicterow.
It was no small achievement for the daughter of Khondaker Hossain, who moved to the United States from Bangladesh 11 years ago when Farah was a baby. Her last name is different from his, following a Bangladeshi tradition for naming girls.
"I didn't know what composing was, but I loved it right off the bat," said Farah, who got her first taste of writing music after the program visited her public school four years ago.
Her family lived in Queens, and he worked odd jobs. Last year, Hossain became an NYPD traffic agent.
His wife, Shaheen, stays home and takes care of the family, whose members now live in a luxury high-rise behind Lincoln Center that offers some apartments at affordable rents; they won theirs by lottery.
Another daughter, 18-year-old Sarah, attends Columbia University on scholarship.
Farah's electronic piano stands right outside the bedroom the sisters shared until Sarah went to college. An image of Hannah Montana hangs above the desk with other pop stars, but since she started writing music, Farah also listens to Beethoven and other classics with her family.
The budding composer, barefoot and in jeans, walked up to the black-and-white keys to improvise some new melodies, with some Asian-sounding intervals echoing the music of her roots.
She has not been back to Bangladesh since her family left Dhaka, the capital, but said that "Serenity" was inspired by her parents' stories about her native land in their Bengali language.'
"It begins quietly, then it gets crazy and out of control, like the busy feeling of Bangladesh, always on the move," she said. "And then it goes back to quiet."
Farah, who attends a gifted children's school at Manhattan's M.S. 54, started composing at P.S. 199, where Deak - also a composer - introduced his Very Young Composers program, sponsored by the orchestra.
The kids played their recorders to try out tunes, and even if they didn't know how to read or write music well, they were helped by composer Paola Prestini to write down what they sang, played and clapped out.
"Real music is happening on the streets every day - kids pound, they sing, they dance. I want to bring that in - the raw sounds that come out of children's voices," says Deak, 64. "I'm looking into their hearts. That's the miracle."