In 2014, Ms. van Kampen took her play to Dominic Dromgoole, then the artistic director at the Globe. “He said, ‘The bit I’m interested in is Farinelli, and if you do it, I’ll put it on,’” Ms. van Kampen recounted. She didn’t take him seriously, but shortly thereafter discovered that the play was listed in the Globe’s new season brochure. “Then I had to do it!” she said with a laugh.
“More seriously, I think I’ve always responded to people asking me to do things,” she added. “Perhaps Dominic thought it would be a collection of arias with a few words between. I don’t think he thought it would be a fully fledged play.”
Ms. van Kampen does use arias of the period, by Handel and Porpora, to both punctuate and accelerate her fully fledged play, mostly set in 1737, when Farinelli, invited by Elisabeth, the wife of Philippe, arrives at court. He immediately establishes a bond with the afflicted monarch (played by Mr. Rylance), first seen fishing from a goldfish bowl in his bedroom. The king is profoundly moved, and partially cured, by the purity of the castrato’s voice.
“This is not a straight play, nor is it a musical nor an opera,” said Ms. van Kampen. “It’s a hybrid form of all those things.” (The singer was also the subject of the biopic “Farinelli,” which won the 1995 Golden Globe for best foreign film.)
At first, Mr. Dove said, they weren’t sure how to best stage the singing. He and Ms. van Kampen decided that Farinelli would be played by two men: Mr. Crane, in the speaking role, and Mr. Davies, who steps onstage to sing as his alter ego stands quietly by. (James Hall will also sing the role on days when there are two performances.)
Both subject and form are ambitious, but Ms. van Kampen said she was not nervous about the play’s reception. “I had nothing to lose,” she said. “And once the audience laughed at the first preview, I was fine.”
“Farinelli and the King” won glowing reviews. “A richly unusual evening that not only demonstrates music’s curative power for a mad king but its ability to offer spiritual uplift to just about everyone else,” wrote Michael Billington in The Guardian after the premiere.
Ms. van Kampen, who trained as a pianist at the Royal College of Music, worked as a professional musician until she was 33, when a friend asked her to step in as the musical director for a production at the Royal Shakespeare Company. “As soon as I set foot in there, I knew it was for me,” she said. She met Mr. Rylance soon after, in 1987, and they married in 1989.
When he became artistic director of the newly founded Shakespeare’s Globe, Ms. van Kampen became its musical director, developing an extensive knowledge of Renaissance music. Compared with researching that era, she said, deciding upon the music for “Farinelli” was relatively easy. “The Baroque is not as unfamiliar to us, the orchestra is not very different to today and there is masses of written music,” she said.
Her years at the Globe, she added, also provided “a master class” in dramatic composition and in balancing the needs of music and prose in a play. She wrote and rewrote “Farinelli,” she said, with both Mr. Rylance and Mr. Dove (“absolutely fantastic on dramaturgy with new writers”) as sounding boards.
Mr. Rylance said that although they had talked constantly about the play, his wife hadn’t written it for him. “I don’t think I was initially available,” he said. “When I did join, I don’t think I changed anything, but Claire has known and watched me for a long time. She knows how to write for an instrument. I think she has put in those things I can do as an actor.”
He added, “For me, the essential questions are ‘Why did Farinelli give up the Michael Jackson career that he had in order to sing for one man for so many years?’ and ‘Why was the music healing?’”
The period was fascinating in terms of its attitudes toward mental illness, Ms. van Kampen said. “The church thought of insanity as demonic possession, but there were new approaches, too, like the belief that music could heal. The doctor in the play, very much a man of the Enlightenment, believes this.”
It was therefore vital, she said, that the powerful effect of the voice was dramatically convincing for audiences. Once Mr. Davies had accepted the singing role, she tailored her musical choices to the specific qualities of his voice, rather than trying to imitate the elusive sound of the castrato.
“When Claire rang, I originally thought no,” Mr. Davies said in a telephone interview from New York, where he was appearing in Thomas Adès’s “The Exterminating Angel” at the Metropolitan Opera. “Farinelli was a sopranist, with a much higher range than I have, and I thought a female voice would be better.” Finally, persuaded by Ms. van Kampen that it was the effect rather than strict historical authenticity that mattered, he agreed.
With what he described as “a pretty encyclopedic knowledge” of the period, he helped Ms. van Kampen decide on the arias; they have changed two for the Broadway production and added an additional song. “It’s mostly Handel now because he is really much better than anyone else writing then,” Ms. van Kampen said. (Although Farinelli didn’t sing in Handel’s company, she saw no reason that he couldn’t have learned the songs.)
“I try not to draw focus; I’m a bit like a ghost or a hologram,” Mr. Davies said. “I wouldn’t make the mistake of acting opposite Mark Rylance anyway.”
The arias, Ms. van Kampen said, are not about dazzling the audience with coloratura sound, but about the beauty and healing power of a voice. “The audience coming to the show is primarily not an opera audience,” she said. “I wanted to find something universal. Whether it’s Billie Holiday or Maria Callas or Iestyn Davies; if a voice moves us, we feel it.”