Sean Lennon Recalls Growing Up Next Door to 'Aunt' Roberta Flack: 'Coolest Neighbor in the World'

When Roberta Flack moved into the Dakota in the 1970s, she took up residence next to the New York City apartment building's most famous tenants: John Lennon and Yoko Ono.

Soon, they shared more than just walls, and a decades-long friendship developed between the musicians, Sean Lennon recalls in Roberta, a new documentary chronicling Flack's legendary life that will premiere on Thursday.

"I was very blessed that I grew up with the coolest neighbor in the world," Sean, 47, says in the film. "At first, I didn't even think of Roberta as this incredible artist and musician, she was just this really cool neighbor. We used to call her Aunt Roberta, and we were very close."

The star says Flack, 85, would offer words of encouragement when he started learning to play the guitar, and that she and Ono, 89, became "very good friends" — especially after John Lennon was shot and killed outside the building in December 1980.

"They understood each other because they were both incredibly powerful women," Sean says. "My mom, she'd be in the studio producing my dad's records, and people don't really think about that. They imagine this sort of quiet girlfriend, but my mom is often a dominating force in the room and I think Roberta was just like that. They both dealt with that kind of sexism, but it's something that they overcame, and they were tough."

The pair eventually worked together, too. In 1984, Flack recorded a version of Ono's song "Goodbye Sadness" for the album Every Man Has a Woman, which was made as a tribute to the artist for her 50th birthday.

Ono had originally released the song on Seasons of Glass, her first solo recording after John's death. The album cover famously featured the bloodstained glasses the former Beatle was wearing at the time of his death.

In Roberta, Ono is featured in an old interview, reflecting on the ways in which the "Killing Me Softly with His Song" singer transformed the essence of "Goodbye Sadness" with her soulful voice.

"Mine was trying to go away from sorrow. But in her song, it really sounds like goodbye, sadness, and you really feel that it's gone," Ono says in the documentary. "She has the capacity to take songs as a tool to express herself, but each time she does that, it becomes Roberta."

She continues: "We're very close to each other and our kitchen is connected and there was a beautiful, spiritual exchange working together on this album."

Though they lived as neighbors for decades, Flack listed her Dakota apartment for sale in 2015, and it eventually sold in 2018. Ono still lives in the storied building, which sits on Central Park West.

In 2010, Flack spoke about her time in the Dakota in an interview with The New York Times, saying it was "chockablock full of famous people," but most of them "tend to keep to themselves," including her.

She also recalled watching Sean and John Lennon spend time together, telling the outlet: "Sean loved his dad. There was a lot of holding hands and looking up, and a lot of holding hands and looking down."

Roberta, a feature-length doc, will celebrate Flack's "distinctive voice, songs, piano gifts and her indomitable spirit," according to a press release.

It'll cover her legendary career — which includes four Grammy wins — as well as her work as a civil rights activist.

Its premiere comes the same week a spokesperson for Flack announced that the star was diagnosed in August with ALS, which has robbed her of her voice.

The disease "has made it impossible to sing and not easy to speak," the spokesperson said. ""It will take a lot more than ALS to silence this icon. Miss Flack plans to stay active in her musical and creative pursuits. Her fortitude and joyful embrace of music that lifted her from modest circumstances to the international spotlight remain vibrant and inspired."

"The First Time Ever I Saw Your Face" singer suffered a stroke in 2016, but told PEOPLE in February, before her diagnosis, that she was eagerly awaiting a return to performing.

"The pandemic has kept most of us off the stage for two years," she said. "I don't know what the next two years will hold, but I hope to see my fans in person sometime soon."

Roberta will premiere at the DOCNYC film festival on Thursday and will be available to the public on Jan. 24 as part of the PBS "American Masters" series.