They are called Le Mystere des Voix Bulgares, or translated, “The Mystery of the Bulgarian Voices.”As enigmatic as the name sounds, they are best known for the incredible sounds they produce, particularly when singing the multi-choral folk songs of their native Bulgaria.Composed of 26 performers, this all-female a capella ensemble is touring for the first time in 18 years, making a rare appearance at Milwaukee’s Pabst Theater, Friday, May 16.

  And the music they make is exceptional.Originally known as the Bulgarian State Television Female Vocal Choir, Le Mystere was first “discovered” in the early 1950s by Marcel Cellier, a Swiss producer who visited Bulgaria and was entranced by what he heard. It actually took Cellier 15 years just to produce and press the first recording of the ensemble.

  For over 50 years, the group has continued to attract followers worldwide as diverse as George Harrison, Jerry Garcia, Paul Simon, violin virtuoso Midori and even Goth rocker Peter Murphy of Bauhaus, who passed an unlabelled Le Mystere cassette tape to 4AD record label founder Ivo Watts-Russell. Watts tracked down Cellier and licensed the music he was putting out under the Le Mystere name.

  What makes the sound of this ensemble so unique, so fresh given its folkloric traditions?

  “The quality and volume of the sound is more bright, loud, unique in timbre,” says Dora Hristova, the conductor of Le Mystere. “We have the highest professional level of performance with our vocalization techniques.”

  “We recruit these singers from the villages, from the most distant parts of the country, not spoiled by civilization, urbanization and contemporary media,” Hristova points out. “These singers are born with such physiology to sing with ‘open throat’ techniques. And this tradition is passed over from one generation to another.”

  Today, there are special schools and a university where singers undergo extensive training to learn this style of singing that dates back for centuries, tracing its origins from Bulgaria’s Thracian, Ottoman and Byzantine influences. And even though their native tongue is Bulgarian, the members perform in a variety of languages ranging from Dutch to Hebrew. For a future tour that takes the group to Korea, Le Mystere is preparing to sing a love song in Korean.

  But it is the original music and the precision and prowess of those voices that seduce audiences time and again. “The concert program follows the way of the evolution of Bulgarian traditional vocal music, from the authentic song which is different in style, melody, ornamentation and rhythmic patterns…to the simple harmonies of contemporary Bulgarian composers,” she says. “The most significant point is to preserve the quality of these voices.”

  And hearing the group live only adds to the mystery of those Bulgarian voices. Les Mystere des Voix Bulgares perform at 8 p.m., Friday, May 16 at the Pabst Theater. For more information call 1-800-511-1552 or visit: www.pabsttheater.org.