The human voice is the most basic of all musical instruments. But when singers come together as choirs, quality standards vary widely around the world.
A festival in Washington is bringing together top-tier choirs from a dozen countries in a bid to show music's universality - how the joy of singing together transcends cultures.
But the festival is also part of an effort to boost training for choral music, which can be rudimentary in many countries. The Serenade! Washington DC Choral Festival is the brainchild of Neeta Helms, president of Classical Movements, a company that runs international tours for major music ensembles.
Helms, who launched the festival in 2011, said she had been struck by an explosion of global interest in choral music - largely outside the Western canon. "I'm not on a mission to change the world through choral singing - although I think that sometimes we end up doing that. I've seen a need and I've seen I can help," she said.
"Everybody has a voice - well, almost everybody - and almost every culture has this huge tradition of songs and sounds and rhythms and folk tunes," she said. The latest Serenade festival, which runs eight days through July 4, is part of celebrations for the centennial of the birth of slain US president John F. Kennedy.
With free concerts at the Kennedy Center and other sites across the Washington area, the festival features choirs from countries with strong connections to Kennedy or the Peace Corps, the international volunteer program his administration created. Performers include Mongolian folk group Egschiglen; the Madras Youth Choir, formed by celebrated South Indian film composer M.B. Sreenivasan, and Spain's L'Escolania de Montserrat, considered the world's oldest boys choir - which has ties to cellist Pablo Casals, who was famously invited to the Kennedy White House. Choirs also come from Kenya, Zimbabwe, China, Northern Ireland, Panama, Bulgaria and Latvia - which Kennedy visited while a Harvard student.
Helms, who was born in India, said she saw a particular demand in the billion-plus country where many people without means can instantly sing along to Bollywood hits yet have nowhere to train. Classical Movements has started a fellowship to send established choir directors to India as instructors. As part of the festival, the company also has commissioned original works from around the world.
Members of choirs especially need to master harmony - coming together as a whole by singing different, and often fewer, lines. "I always say that Pavarotti would have been terrible in a choir. His voice would have stuck out," she said.
Choirs at the Serenade festival vary sharply in their traditions. The Mongolians sing from their throats while the Africans often have rich vibratos and, compared with Europeans, dance and move much more when they sing. With choral music often passed down by oral tradition, it can carry more freedom than, say, Western orchestral music, which emphasizes precision.
But Helms said it was also critical to transcribe choral music. "That's how things spread. That's how literature has spread - the printing press was created," she said. "Someone has to take all those folk tunes that are in people's heads, or some records of them, and put them down on paper so that people can figure them out."
But whatever the course of education, Helms said she was impressed by seeing choirs bond - uniting in music without regard to race, gender, religion or other barriers.
"We are firm believers that in this small way we are changing the world bit by bit," she said with a laugh, "no matter who is in power in that country or our country."