Director Alex Waterman and actors Elisa Santiago and Raúl de Nieves at a rehearsal for Robert Ashley's 'Vidas Perfectas.' Andrew Hinderaker for The Wall Street Journal

Near the end of the composer Robert Ashley's life, director Alex Waterman and his actors rehearsed in Ashley's TriBeCa studio, preparing his operas for the Whitney Biennial.

"We were rehearsing on the sixth floor, and he was down on the fourth floor, in bed," said Mr. Waterman. "We recorded things, and Mimi," Ashley's wife, "would take it down. He would listen to it and give comments."

Ashley was more concerned with narrative than musical details. "He didn't want to get in the way of the music-making, but he was very much interested in how the story was being shaped, and shaped by a person's presence," said Mr. Waterman.

Opening Thursday, just over a month after Ashley's death at the age of 83, the Whitney presents three of his operas: "The Trial of Anne Opie Wehrer and Unknown Accomplices for Crimes Against Humanity," "Vidas Perfectas" and the world premiere of the autobiographical "Crash." Ashley is a composer known for radically redefining opera, and there is substantial interest in these works—"Crash" sold out in three days.

But while Ashley's is the boldface name of the productions, the driving force behind them is Mr. Waterman, who for the past 10 years has dedicated much of his artistic life to Ashley's unconventional works and operas, which lack arias, standard musical notation and other usual trappings of the art form.

"That's the genius of Bob's work," said Mr. Waterman, in the Williamsburg apartment he shares with his wife Elisa Santiago, who performs in "Vidas Perfectas," and their toddler son. "His idea of an opera is that it's characters in a landscape telling stories musically."

For Mr. Waterman, a major attraction of Ashley's work is the idea of music as a social and collaborative process, where a less formal interpretation—like that of the performance collective Varispeed, which produced a site-specific "Perfect Lives" in the Catskills—is just as valid as Mr. Waterman's more formal one.

"I'm interested in music not just as a way of organizing sound," said Mr. Waterman, "but as a way of thinking about who we are when we gather together, and how we listen and speak together, and how we produce things together."

In addition to directing the operas, Mr. Waterman raised over $55,000 on Kickstarter, and has overseen nearly every aspect of the Whitney productions and the continuing creation of a television version of "Vidas Perfectas."

"Normally there are teams of people doing what Alex is doing," said production designer Sean Daly.

Mr. Waterman, also an artist, musician and self-described "long-form person" who is drawn to big projects, first fell in love with Ashley's work in 2004 when he encountered trios that are to be printed with three types of white ink on an off-white page. "I was captivated by this idea," he said.

A decadelong collaborative friendship ensued. Mr. Waterman is finishing a 750-page book on Ashley, in addition to a doctoral dissertation on "an idea that could be credited to Bob."

"He gave me access to everything," Mr. Waterman said. "I've never had that experience with another musician or composer."

In the process, he absorbed Ashley's work. "Even the cadence of Alex's voice can be similar to what Bob's voices sound like," said producer Alexandra Rosenberg.

"He knows every nuance of this," said Ned Sublette, who stars in "Vidas Perfectas," and was the cue-card flipper for Ashley in the original "Perfect Lives."

Mr. Sublette continued: "He's thought about the minor elements in the text and how they relate to structure and visual motifs. He's got a very complete vision."

At a recent "Vidas Perfectas" rehearsal, the actors sat around a table in Mr. Waterman's living room, in front of empty coffee mugs and a bowl of Doritos. Mr. Waterman was more facilitator than director, merely watching while actors debated the rhythm and pronunciation of a single word.

Over an electronic track and the pianist's improvisations, a kind of Afro-Cuban jazz meets poppy American dance music, Mr. Waterman conducted the chanting and singing, occasionally offering a grin or thumbs up.

"This is an incredibly mystical text," he said.

—Where to hear and see: April 10-27; Whitney Museum of American Art, 945 Madison Ave.; 212-570-3600;