With 8,000 pages of transcripts, it took Mr. Roth a year to extract the 600-or-so snippets of talk that held promise, and then years more to assemble them into a compelling picture. “I’m excited for people to know more about these two people,” he said. “I grew to love them even more in doing this.”

On the first day of rehearsals in August, the actor Leslie Jordan said he already has a deep connection to Capote. As a little boy who was taunted as a “fairy,” he said, seeing the flamboyant author on TV triggered such a shock of recognition that Mr. Jordan ran to the bathroom to vomit. He could hardly be more perfectly cast for the role, he said: “I’m Southern, I’m gay, I’m little – I get Ma’am’d a lot on the phone.” (On Sept. 7, Mr. Jordan withdrew from the production for personal reasons. Dan Butler will play Truman Capote instead.)

Opposite him onstage (Michael Mayer is directing) will be a Warhol played by Stephen Spinella, a two-time Tony winner for “Angels in America.” As Mr. Jordan told his bathroom story — hamming it up, Capote-style — the lanky Mr. Spinella listened in silent, Warhol-ish observation.

He said he didn’t have such a personal connection to his character, partly because of his admiration for him: “I’m playing somebody who has a way of seeing the world that is so much more interesting and revelatory than the way I see the world.” His challenge, said Mr. Spinella, would be to reveal a “real” Warhol inside a creator so controlled and self-conscious that he was always playing some kind of part.

Mr. Roth’s own crush on Warhol blossomed when he first saw the artist assuming a role. In 1985 Warhol appeared, as some version of himself, on “The Love Boat,” a favorite TV program of Mr. Roth’s throughout his youth in New Jersey. “I related to him — an outsider, a geek,” he explained.