By James Reaney

The spectacular sound of le Mystere des Voix Bulgares is famous around the world.

The look of the acclaimed Bulgarian vocal ensemble is also totally its own. Brown in the folk ensemble's stage costumes is for the mountains of their Balkan homeland and yellow and green is for Bulgaria's valleys.

Then, there is red in many vivid hues.

"The red is the colours of the heroic movement... the blood," says long-time conductor Dora Hristova.

In symbolic regional terms, those reds also pay tribute to hilly Thracia and to the blood that was spilled defending Bulgaria against the Ottoman Turks.

Hristova has been directing her singers since 1988.

"At the beginning, I didn't think it would be so long, to be popular for so long, for 20 years," she says.

Tomorrow, Hristova brings the 23 females and two males of le Mystere to London for the first time. The Bulgarians perform in a Sunfest World Music & Jazz '08 series concert at Aeolian Hall at 8p.m. London Pro Musica, a concert co-sponsor, also performs.

"We have two boys, male voices, who perform the songs (representing) the male tradition," Hristova says. That corrects the impression that le Mystere is all female, all the time.

"No pianos, a cappella, a cappalla singers all the time," Hristova says.

The Grammy-winning choir is based in Sofia, Bulgaria's capital. Its arrangements are kept in confidence by the ensemble, which rarely changes members. The women rehearse together, live together and tour together, celebrating birthdays and namedays on the road.

"We all live in Sofia, but some of the girls were born in the villages," Hristova says.

Kepping le Mystere on the road is expensive and singers rely on income from other sources, says the conductor.

"Some of the girls are teachers, some of them have a private business," Hristova says.

Originally known as the Bulgarian State Radio and Television Female Vocal Choir, le Mystere (or the Mystery of the Bulgarian Voices) brought its world music to the U.S. in the 1990s. The choir won a 1990 Grammy for best traditional folk album, leading to an appearance on the Tonight Show, and a Grammy nod for its 1994 album Rituals.

It's folk songs can be hundreds of years old, but Hristova and others bring them into the contemporary world. Le Mystere's arrangements reflect the ancient music's dissonance, rhythms and microtones that tie Bulgarian folk music to the progressive Western classical world's sonic universe.

One listener hears "an archaic world of sounds from times long ago." Another hears "the marriage of the avant-garde and the Middle Ages."

Rave reviews are a regular event for le Mystere.

"Breathtaking in its sublime beauty," is one rave from the Los Angeles Times that does full justice to the group's accomplishments. "Employing vocal techniques that defy western traditions of voice production, the singers juxtapose flat, nasal tones with full round ones; dissonant, unearthly harmonies with consonant blends right out of Christian hymn; slow trance-like shifts in texture and harmony with compley, percussive, rapid-fire rhythm."

Le Mystere is making its eighth North American tour. The only other Canadian stops are in Montreal and Toronto.