They've backed pop diva Beyoncé at this year's Oscar ceremonies seen by hundreds of millions of TV viewers. They've provided the ethereal choral sound behind Kodak's "True Colors" ads. They've sung all over the world, on their own and with orchestras such as the New York Philharmonic and the Philadelphia Orchestra.
Few would dispute that the American Boychoir is one of the best choirs in the world. Although their musical form embodies nearly a thousand years of European tradition, the choir is also utterly American in its approach.
At least two decisions have led to the choir's signature sound, which reviewers have called "honey-toned," "achingly pure," "electrifying," and "angelic." The first involves training that promotes "free singing" and allows a hint of natural vibrato in the voices. The second is a commitment to keeping boys in the choir past the time when their voices begin to change.
British boy choirs "have a very different approach to sound: It's a very pure, straight tone," says Fernando Malvar-Ruiz, the choir's music director. "They don't have any vibrato because they are controlling that sound."
That approach works well in cathedrals where these choirs usually perform, he says. The American Boychoir, by contrast, sings in a variety of settings.
"I think it's that roundness [of tone]" created by free singing that gives the choir its unique sound, he says.
About 60 students, Grades 5 through 8, are trained at the choir's school in Princeton, N.J. Most are boarders, though some come from surrounding communities.
In traditional European choir schools, boys whose voices begin to deepen and mature are asked to leave immediately. But the American Boychoir School has taken another, more inclusive direction.
"I believe the changed voices can add a lot to the choir, not only in terms of musicianship but in terms of sound," says Mr. Malvar-Ruiz. "It's a bit husky, but ... you learn to love it."
In the fall, the choir usually performs only pieces for high voices: 1st soprano, 2nd soprano, and alto (or, in boy choir nomenclature, 1st treble, 2nd treble, and alto). During the school year, as some voices mature and deepen, pieces are added for soprano, alto, tenor, and bass. At a recent concert in Boston, the choir sang the Hallelujah chorus from Handel's "Messiah" with all the parts as written.
Though boys through the age of 12 or 13 can sing in the same vocal range as women, their sound is unusual. Some listeners find it almost otherworldly.
"Physiologically, there is a difference between a male treble and a female treble," Malvar-Ruiz says. "The larynx is formed differently, so the girls have a bit more airiness to the tone. The boys have a very pure sound ... unlike anything else you hear."
On July 8, the choir will help open the season at the Tanglewood Music Festival in Lenox, Mass., the summer home of the Boston Symphony Orchestra. The Boychoir will join maestro James Levine and the Boston Symphony and Tanglewood Festival Chorus for a massive production of Mahler's Symphony No. 8.
But even that rarified atmosphere may not compare to the thrill of performing at the Academy Awards ceremony in Los Angeles last February.
Clifford Weekes, a sixth-grader from New Jersey who sings treble and was steaming the wrinkles out of costumes backstage at the Boston concert, says Beyoncé talked with him and even asked his name. "We met Morgan Freeman, too," he added. "He gave us high fives. We saw almost everyone."
Aaron Davis, an eighth-grader from South Carolina who sings alto, will end his boy-choir career with this summer's Tanglewood event. Besides the Academy Awards, he's traveled to Latvia and Scandinavia. Now his sights are set on becoming a conductor.
No more than 10 percent of the boys are likely to go on to careers as professional musicians. But all gain precious experiences. Whether they will have outstanding adult voices varies from boy to boy. "They will have the technique," the director says. "Whether the voice accompanies that, that's just however they develop. But the technique will be there.... They will know how to sing."
The 10- to 14-year-olds receive four hours of conventional schoolwork in the mornings. After lunch and intramural sports, they study music theory, break into groups for sectional rehearsals, and then combine for an hour rehearsal of the full choir.
Many recruits are drawn from young audience members who see the choir perform on tour. Auditioning is a simple process, lasting only one to four minutes, Malvar-Ruiz says. No previous vocal training is needed, and in fact poor training is worse than none at all.
"I look at raw qualities - good ear, good voice," he says. "I don't look at technique or musicianship because we can train that."
Most of all, he seeks a passion for singing. "That's what is going to get you into this choir more than anything," he says.