Bulgarian Vocal Ensemble Back to the Tried and True : Music: After experimenting with more modern styles following the country’s political changes, Le Mystere des Voix Bulgares returns to its ‘universal music.’

Like virtually every other Eastern European institution, Le Mystere des Voix Bulgares--the haunting Bulgarian women’s vocal ensemble--got swept up in the wave of modernization that came after the fall of communism.

Last year the group even lent its unique sounds to an album of techno-dance music, “From Bulgaria With Love,” in which various European producers incorporated the voices into bubbly electro-pop creations with such winking titles as “Guns and Paprica” and “Sofia Sound Machine.”

But as with other forces of change in the region, this move led to a tug-of-war with hard-line traditionalists. In this case, one of those resisters was the one with the final say: Tanja Andreeva, the choir’s impresario. Though proud of the dance album, she’s put the kibosh on any more such ventures.

“I don’t think there will be any other experiments,” she said firmly in a recent phone interview from her home in Sofia, noting that she regularly receives offers for various non-traditional projects. “The main direction is we keep the line where we feel really strong.”

That line involves otherworldly a cappella harmonizing--from sweet to shrill--in formalized settings of folk melodies from mountain villages. Though Andreeva actively commissions new compositions, the style is still largely based on models set out more than 40 years ago by Bulgarian composer Phillipe Koutev.

It’s what will be heard in the group’s concerts Friday and Saturday at the Westwood United Methodist Church, part of a cathedral-oriented tour following a live album, “Melody, Rhythm & Harmony,” recorded earlier this year in a cathedral in Norway.

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That sound became an unlikely must-have “discovery” for cutting-edge pop fans after England’s 4AD label released “Le Mystere des Voix Bulgares,” an album by the Bulgarian State Radio and Television Female Choir, in 1986, and Elektra issued it in the United States a year later. The album shot up the world music charts, which had generally been dominated by rhythmic reggae and African releases, and a U.S. concert tour drew rave reviews.

But even then the music’s success was generally dismissed as an attractive novelty that would soon fade back into the ethnic-music woodwork. Instead, it’s had surprising staying power, spurring the release of similar recordings and even the use of the sound in several films and television commercials.

That very success is what convinced Andreeva that the old way is the best way.

“I think the secret of the success we should look for is the music itself, the masterpieces of the compositions and the exceptional, unique way of singing,” she said. “There are a lot of elements to it. A lot of people say this is universal music.”

The transition in Bulgaria from communism to democracy, though, has led to changes in the way the group operates. The state-run choir was recently disbanded and Andreeva took 10 of the singers with her to start a new group. She says it’s a great relief to be able to manage the group without the government looking over her shoulder.

“The political changes are not going at the speed we want,” she said. “But this is not as terrible as it was a few years ago. We are free to work at our private pace the way we do now.”

But she still insists that she feels no need for new directions.

“Not for a single moment,” she said. “I know what we are singing, you cannot get tired of.”