THE OPENING SCENE'S haunting music heralds the impending tragedy. A trio of women's voices blends with those of a group of shirtless men filing onto the stage; on their shoulders they carry a stony-faced king on a throne. The lyrics are in an unfamiliar language, but the swelling music and the actors' demeanor make one thing clear: This story is not going to end well.

Argentine composer Mariano Vales wrote both the songs and background score for the Washington Shakespeare Company's production of "The Royal Hunt of the Sun," Peter Shaffer's 1965 clash-of-cultures drama about the conquest of the Inca Empire by Spanish conquistador Francisco Pizarro (James Foster Jr.). The aging Pizarro, greedy for the Incas' gold and charged with seizing the empire for his country and the church, finds his world shaken to its foundations when he meets Atahuallpa (Peter Pereyra), the Incan king.

When Vales met "Royal Hunt" director Steven Scott Mazzola in November, "something just clicked," Vales recalls. Mazzola told him about his idea to produce Shaffer's play, and Vales eagerly signed on to pen the score.

But there were obstacles to overcome in mounting the drama, especially at the troupe's intimate Clark Street Playhouse in Crystal City. One scene depicts soldiers crossing the Andes Mountains, another the massacre of 3,000 Incans. Vales says that staging the play on the company's shoestring budget was a daunting -- and irresistible -- challenge. Shaffer himself recognized these challenges: In a 1965 story for the New York Times, he wrote that a playwright's role is "exercising the imaginative muscle of his audience," referring to "Royal Hunt" as "an experience that is entirely and only theatrical. Total theater." His play criticizes "the neurotic allegiances of Europe, the Churches and flags, the armies and parties," but it's also the story of one man's quest for immortality.

In Buenos Aires, Vales worked in theater, writing musicals, composing scores and even setting Shakespeare to music. But in the late '90s, Vales, his wife and infant son moved to the United States so Vales could earn a master's degree in conducting at Yale. A few years after moving to Washington, he was eager to get back into theater and writing. "I missed composing," he says.

His work on "Royal Hunt" is, for the most part, a departure, though it's hard to pigeonhole the Argentine. Among his interests is the Washington Saengerbund, a choir he conducts that performs traditional German folk and classical songs. He is also the musical director of Musica Aperta, which Vales describes as an experimental mix of music, theater and food. "We use other arts to give context to the music we're performing." (A show at the Shakespeare Theatre last fall, for example, served upbeat waltzes and homemade sorbet at intermission.)

"Royal Hunt," too, draws on multiple sources of inspiration. Vales says the score is intended to "highlight moments through music: the greatness of the Incan empire, the solemnity of the church, the strain of mountain climbing. It gives it a cinematic element."

The music features lyrics in four languages -- English, Spanish, Latin and the indigenous Peruvian language of Quechua -- with South American and European instrumentation, including pan flutes and drums. Vales assembled the Latin lyrics, for example, from various liturgical hymns, the words adding meaning to the scene. When the Spanish soldiers are at Mass to consecrate their journey to the New World, the accompanying song's lyrics ("Thou shalt make them princes over all the earth . . . ") are from a medieval ecclesiastical text.

Vales wrote the Incan songs using the pentatonic scale, with intervals commonly used in traditional Andean folk songs. One of them, employing a 16th-century poem describing the atrocities of Pizarro's army, was the product of Vales's extensive research of historical texts.

The emotional climax of "Royal Hunt" is accompanied by deep, rich drumming and a mournful, searing melody. It is a moment of high drama that owes much of its heart-rending intensity to Vales's music, which underscores the central conflict of the play -- Pizzaro's fascination with the charismatic Incan king juxtaposed with the Spaniard's painful betrayal of his new friend.

But while "Royal Hunt" is riddled with conflict, the drama's staging was relatively trouble-free, according to Vales. "It was a smooth process. Steven [Mazzola] took care of all the details." He praises the director's talent and demeanor, saying: "He has such an open mind; he's such a sensitive director. There's not many like him."

Though Vales says he'd like to work with Mazzola again, he's already working on his next project, without the director. Harking back to his years writing musicals in Argentina, Vales has just finished "a musical farce on Argentinean politics"; the score will have a distinctively Latin American flair, including tangos sung in English. He is looking for a producer to finance the show.

Despite his next project's subject, Vales denies that the staging of "Royal Hunt" had anything to do with current events. "There's nothing that we did to try to relate it to any politics," he says, adding, "It's just art for art itself."

Peter Pereyra plays Atahuallpa, the Incan king, in Peter Shaffer's drama "The Royal Hunt of the Sun" at the Washington Shakespeare Company.James Foster Jr. is the greedy Pizarro in "The Royal Hunt of the Sun."