In May, musician Matt Marks died suddenly, of heart failure, after a performance with the ensemble Alarm Will Sound.

It was a blow to the tight-knit world of contemporary music, in which the 38-year-old Marks was a prominent presence as a composer, vocalist and French horn player. Along with his prolific compositional output, he helped found Alarm Will Sound, as well as the New Music Gathering conference, and he was a provocatively humorous mainstay on social media.

This community rallied to memorialize him. Alarm Will Sound started the Matt Marks Impact Fund to develop new works. Several of his close friends completed his score for a theatrical piece, “Words on the Street,” which had its debut in October. And Tuesday at Roulette in Brooklyn, the Prototype: Opera/Theater/Now festival — which presented Marks’ opera “Mata Hari” in 2017 and runs through Jan. 13 — will revive his breakthrough 2010 work, “The Little Death: Vol. 1.”

Marks’ fiancée, composer Mary Kouyoumdjian, has become the de facto steward of his musical legacy. “I don’t want him or his music to be forgotten,” she said in a recent interview. They had been close artistic collaborators, sharing drafts and producing each other’s recording sessions.

“He was such a strong advocate for my own music and getting it out there,” she added, “that this is the smallest way for me to return the favor.”

Much of Marks’ music draws together a permissive polystylism with a comedic irreverence toward the ritual trappings of classical music. In a 2016 recording he posted on SoundCloud, he dramatically — and hilariously — recited pianist Khatia Buniatishvili’s hagiographic website biography atop the majestic theme from “Jurassic Park.”

But his death has also brought into stark relief the intense intimacy that is the basis of several of his works, which were conceived during — and are partly about — personal relationships, and which now have a new emotional rawness. This is particularly apparent in the coming production of “The Little Death,” which Marks originally created in close collaboration with soprano Mellissa Hughes while they were dating, and which has not been performed since they broke up in 2012.

“I viscerally got sick,” Hughes recalled in an interview about being asked to revive the work at Prototype. “I couldn’t think about doing it, and it just felt wrong.”

In 2006, as young New York-based classical music freelance artists, Marks and Hughes met on a bizarre gig: a PBS crossover special being filmed in Miami, in which their live performance was replaced by canned audio. They reconnected on Myspace, where Marks had posted some simple songs he had written.

As they began dating, Marks’ compositions became more serious, and he increasingly wrote specifically for Hughes’ voice, culminating in “The Little Death.” Starring Marks and Hughes and billed as a “post-Christian nihilist pop opera,” it presented a love story of religious and sexual awakenings reinforced by Marks’ intricately wrought, omnivorous score: One exuberant duet combines electropop and the shape-note hymn “Wondrous Love.”

A series of grandiosely cheeky performances in various spaces in New York, and a recording released on New Amsterdam Records in 2010, were heralded for embodying an emergent genre-crossing scene widely known as “indie classical” or “alt-classical.”

Marks and Hughes worked on Vol. 2, but the project ended with their relationship. “I haven’t even sung through any of it or even really hummed through it since 2012,” Hughes said. “When you create something like that with somebody, it becomes a part of you, and so when you’re no longer with that person, it’s hard to revisit.”

Electronic samples on the album, and passages in Marks’ libretto, memorialize inside jokes and moments in their real-life romance. “When I hear these things, it’s hard to remember,” Hughes said. “It’s like an audio graveyard.”

“But it’s also beautiful,” she added. “It was a time in both of our lives that we were so creative, and we were young and poor and nobody knew us, and so we didn’t care. We wrote what we wrote.”

That sincerity was a through line in Marks’ music and motivated his exhaustive engagement with musical genres that might be looked down on by other composers. “One of the things that I respect about Christian music and Christian pop music is that they’re willing to get sentimental,” he told The Brooklyn Rail in 2010. “I think you can actually mess with people’s heads way more by going the sentimental route, playing with their heartstrings.” Since his death, moments on the “Little Death” album that might have once sounded arch — hokey chord progressions, campy melodic hooks — can unexpectedly arouse tears.

And at the core of Marks’ compositional voice was his actual voice: a shape-shifting but always identifiable timbre that traversed a range as broad as his musical influences, whether the guttural bellows of his bonkers cover of the novelty song “Donde Esta Santa Claus” or the sickly sweet falsetto deployed to embody a Karen Carpenter-obsessed, disaffected teenager in “A Song for Wade (This is not that song).” With his death, that irreplaceable component of much of his music is gone.

“So many of the pieces that he wrote for himself to sing, it would not work without him,” said composer Ted Hearne. Hearne sang in a “praise choir” assembled to accompany an early run of “The Little Death” and will take on Marks’ part for the Prototype revival. Since the piece lacks a fully notated score, Hearne is learning the music primarily by listening closely to the album.

“I have to be able to perform it with as much confidence and moxie and guts as he would,” he said. He helped persuade Hughes to sing, telling her, she recalled, “If you don’t do it, the piece dies with Matt.”

“The Little Death” was Kouyoumdjian’s first introduction to Marks’ music. She was so captivated by a 2010 performance that, as she was leaving the concert, she walked into a glass door and broke her nose. She and Marks met a couple years later to discuss a potential collaboration with her ensemble, Hotel Elefant, and began dating. (That project was recorded before Marks’ death and will be part of a future release of his music on New Amsterdam.)

Marks was a longtime resident of Brooklyn, and he and Kouyoumdjian would often visit unfamiliar parts of the borough. One such excursion involved a bus trip — during which they shared a pair of headphones to listen to Mariah Carey — to the serene Salt Marsh Nature Center in Marine Park. Not long afterward, Marks began a new project, the pop monodrama “Headphone Splitter,” which takes a lightly fictionalized account of their date as its point of departure: The characters Matt and Baby cozily split headphones on the B41 to go bird-watching on a lazy Saturday and witness a brutal ax murder.

“Having this sixth sense of twisting everything sweet into something really dark, he thought, ‘Oh, this would be the perfect beginning for this murder mystery,'” Kouyoumdjian said. With director Nick Leavens, “Headphone Splitter” was to be developed into a series of music videos driven by Marks’ singing, although he only recorded the first three episodes.

In Chapter 1, atop swirlingly catchy electronics, Marks narrates the bus adventure with his characteristically zany swagger — “Baby, go on, pull out your headphone splitter. Sit close, we’ll listen to the soundtrack of ‘Glitter'” — followed by the sudden homicide. “It has so many elements of things Matt that loved so much,” Kouyoumdjian said: Brooklyn, low-budget horror films, macabre humor.

“The music that he was writing more recently goes back to the music he was writing for ‘The Little Death,'” Kouyoumdjian added, “projects like ‘Headphone Splitter’ that really celebrated him as a composer-performer, and were projects that he could do on his own. He could write his own text, which was something he loved; he could direct the idea and the vision of the project; and he could just sit at his computer and write and produce.”

She is planning to release the two other episodes Marks completed, and she may finish some of the rest of the series herself, although a crowdfunding campaign to support the project did not meet its goal. While Kouyoumdjian has been active as a composer — she has collaborated with the Kronos Quartet and is preparing a commission for the vocal ensemble Roomful of Teeth — she has lately focused more on tending Marks’ body of work.

“It’s a lot easier for me to put energy toward his projects happening, at this point, than for my own,” she said. “Composition is really tricky. It really requires a lot of emotional vulnerability, and I think that that’s a space that’s difficult to be in for long periods of time after you lose somebody.”

“Helping Matt’s music be a little more public,” she added, “is my way of still doing creative work, but in a way that feels right to me, right now.”

This article originally appeared in The New York Times.