NEW YORK, NY.- In the early hours of Jan. 30, 2021, the visionary hyperpop producer Sophie was living in an apartment in Athens, Greece. To get a better view of the full moon, she climbed up a balcony, but slipped and fell. She was 34, and her death brought an outpouring of appreciation for the ways her sonic vocabulary — pointed, wriggly, blippy synthesizer tones and ultra-succinct hooks — had moved so quickly from pop’s experimental fringe to the mainstream.

In Athens — and before that in Los Angeles and London — Sophie had been working on the successor to her 2018 album, “Oil of Every Pearl’s Un-Insides” and its 2019 remix LP. The new album was so close to completion that Sophie had chosen the full track list. Three years later, Benny Long, her brother and studio manager, has finished it, striving to honor Sophie’s artistic intentions. It will simply be titled “Sophie.”

“There was, at the start, a lot of self-doubt: Can I? Is this going to be possible without her?” Long said in a video interview from Los Angeles. “But I thought, really, it comes down to, would she want this album to come out or would she not? And she definitely would.”

Sophie left behind many more tracks in progress, some of which are likely to emerge as singles or EPs, or appear on other performers’ albums. But as a guardian of Sophie’s catalog, Long has decided that “this is the last Sophie album,” he said. “This is an album that we had worked on for years. We discussed everything about it — the themes, the track list. So to do another album and put it out as a solo album, it would just feel all wrong.”

“Sophie,” out Sept. 27, is the artist and producer’s most collaborative album. It includes vocals from songwriters and singers Kim Petras, Bibi Bourelly, Hannah Diamond, Cecile Believe, Jozzy, Big Sister and Liz, as well as the duo BC Kingdom (who have recorded with Solange Knowles). There’s even a spoken-word appearance by DJ and producer Nina Kraviz.

Completing the album became a family project for Long and his sister Emily Long. She studied music law to work with Sophie, and she passed the bar exam two weeks before her sibling’s death. Once Benny resolved to finish Sophie’s album, Emily joined him in making decisions. “Every single day we talk about Sophie and what she loved and the things that would make her happy,” Emily said via a video call from Los Angeles. “We all know why we’re here. We’re all here for her.”

Benny had mixed tracks with Sophie for her previous albums. For the final album, “the sound design and everything, all the compositional ideas, were all there,” he said. “All the layers within each song were already there in some form.”

But, he added: “Sophie would never want to finish anything. She’d always want to move on to the next thing. She was just wanting to create, create, create, which now I’m super thankful for. But at the time I was like, ‘Should we not just finish this?’”

Making the final version of “Sophie” involved “honing certain sounds that I know Sophie wasn’t happy with,” he said. “Or she was happy with this part of a song, but not that. We’d been working on it and discussing it for a long time. So I feel like I had pretty clear in my head the direction she wanted.”

The songs on “Sophie” were “all in very different places,” he said. Some required fixing or rerecording vocals; others involved honing the drums sounds or “just making it punch more.”

Sophie was born in Glasgow, Scotland, and was immersed in music and visual art throughout her childhood. She studied piano and guitar before turning to electronic music and embracing purely synthetic sounds; the only physical sounds on “Sophie” are the vocals. “As soon as she started making music herself, she would always talk about wanting to create something that hadn’t been heard before, and to create joy and surprise and all these human emotions,” Emily said. “I think she felt very free with electronic music to be able to do that.”

From her emergence in the early 2010s, with cheeky, minimalist earworm singles like “Bipp” and “Lemonade,” Sophie’s productions were head-turning, futuristic and influential. They embraced pop hooks even as they warped every sonic parameter: pitch, speed, meter, timbre.

Sophie’s music could be perky or assaultive, skeletal or lavish, flippant or heartfelt, and it could shift in an instant. In 2015, Sophie told Rolling Stone, “The challenge I’m interested in being part of is who can use current technology, current images and people, to make the brightest, most intense, engaging thing.”

Along with her own releases, Sophie worked on productions for Charli XCX, Madonna, Vince Staples and members of the PC Music collective, a group of friends who emerged in 2013 as a hyperpop idea factory. Sophie also presented a distinctive visual aesthetic: plasticky, gleaming and abstract.

Early in her career, Sophie carefully shrouded herself within her music: DJ-ing in darkness and evading photographs. But with the lofty 2017 single “It’s OK to Cry” and with “Oil of Every Pearl’s Un-Insides,” Sophie exultantly revealed her face, her voice and her identity as a trans woman. In her music, and in extravagant stage productions, Sophie made it clear that she would treat gender as fluidly as sound. One title Sophie had considered for the new album was “Trans Nation,” Benny said.

“An embrace of the essential idea of transness changes everything because it means there’s no longer an expectation based on the body you were born into, or how your life should play out and how it should end,” Sophie told Paper magazine in 2018. “For me, transness is taking control to bring your body more in line with your soul and spirit.”

The tracks on “Sophie” trace a four-part arc; its double-LP release places them on separate vinyl sides. “Sophie” unfolds from somber introspection and noisy abstractions — like the buzzing, ratcheting, whipsawing “Plunging Asymptote” (with writer and artist Juliana Huxtable), which often sounds like the teeth of a giant comb being strummed — to jubilant pop self-affirmations with titles like “Live in My Truth” and “Exhilarate.” It then moves into the clubland kicks of house and techno, and concludes with reflections on time and eternity.

“Musically, absolutely, this is her,” Emily said. “Her No. 1 thing was hating nostalgia for the sake of it. She was always more excited about the future. And that’s the heartbreaking thing, but also the thing where her music can give me hope that she can be present. I think if this album does anything, it’s about her legacy not being associated with something purely in the past. That’s my real hope. I think that there’s a part of her in the future.”

Some tracks had been germinating as far back as Sophie’s 2015 debut album, “Product.” Their elements had been tweaked and retweaked as Sophie tested them constantly in her DJ sets. Others were more spontaneous; Benny said that the techno section of “Sophie” was created largely on the spot, as live mixes. “Sophie was always evolving, always changing her set up, always trying,” he said. “‘How can I communicate more directly with my audience? How can I have a recording session that’s more fun?’ She didn’t want to have everything in black-and-white stages — this is the recording, and now we’re going to do the mixing. She was like, ‘No, why can’t my studio session be like a party?’”

Two of the album’s songs, “Live in My Truth” and “Why Lies,” were written and initially recorded one night at a house party in an Airbnb while Sophie was on tour. “She’s like, right, let’s make a song about this,” Benny said. “We still have the mics recording people screaming in the background.”

“Reason Why,” the first single from “Sophie,” features BC Kingdom and Petras; Sophie turned a wordless vocal line Petras recorded while warming up into the song’s hook. In an interview from Los Angeles, Petras, who is trans, recalled Sophie as “the first trans artist friend I’ve ever had.”

“I think we both really related to the alienation that you face, especially in the music industry, and people’s perception of you, and talking about it behind your back, and not knowing how to deal with trans people,” Petras said.

She added, “Sophie was just really radical — and not afraid to put that into the music.”

With Sophie’s death, some of the songs took on new significance. “Always and Forever,” a paean to “shining together” and “transcending time,” now feels like a fond elegy, complete with churchy organ chords. It features Hannah Diamond, who emerged with PC Music. “Everything’s moving away, further and further away,” Diamond sings in a fragile, otherworldly voice.

In a video interview from London, Diamond recalled that the song grew out of a long text chat about the excitement and communal spirit of PC Music and early hyperpop experiments, about how “we made this thing together and it was so special and precious and important.”

Diamond explained that Sophie was backstage the night she made her debut as a singer. “All of my friends and all the rest of the people from PC, before I went onstage, were thinking, ‘Oh, my God, is Hannah going to be OK? Can she do this?’ Because I was so painfully shy,” she said. “And Sophie just sort of pushed me out onto the stage, gave me a little pat on the back and said to everyone, ‘She’s going to be fine. She’s a pop star.’”

“Sophie would encourage people to be the biggest, brightest form of themselves,” Diamond added. “With Sophie it was always like, ‘If I’m winning, everybody’s winning. We’re all going to win together and we uplift each other.’”

During the peak of the pandemic, Diamond cycled across London to spend a day together in Sophie’s home studio, “drinking iced coffee, lying around in her bedroom, writing the song, recording some rough vocals and just basking in friendship,” she said. “It ended up being the last ever day that I saw her in person.”

She remembered biking away, and waving back at her friend. “Sophie just stood in the middle of the street in this incredibly glamorous outfit, smoking a cigarette, looking like this complete vision of beauty, in complete calmness in this crazy time,” she said. “And she was just grinning at me and waving. And, yeah, I think about that a lot.”

This article originally appeared in The New York Times.