The naked voice, crying out at the dawn of civilisation. Jesus being hammered on to the cross (in the film Jesus of Montreal), and all those apples being hand-picked in those sunny orchards to make all those flagons of cider (in the Bulmer's ad). Bulgarian singing is primal stuff, alright - an impression the Improvised Music Company's Gerry Godley did not dispute when, introducing Le MystΦre des Voix Bulgares as part of his Routes in Rhythm series, he proudly pointed to a stage bare of instruments.

The 27 singers file on to the stage sporting "national dress", and hatted with Carmen Miranda-style flower arrangements. They group and regroup, turning to each other and smiling choreographed smiles, to the baton of an uncredited conductor.

The unvarnished voice of the Bulgarian people? Get a life.

Or get a programme. The extraordinary choral works which Le MystΦre perform are contemporary compositions in a folk idiom, or contemporary arrangements. The pioneer in this work - a kind of Seβn ╙ Riada if you like - was Phillip Koutev, one of whose arrangements ended the concert.

Using the co-ordinates of Bulgarian folk music - women's harmonies, dazzling rhythmic shifts and that aching, ornamented sean n≤s voice, he fashioned works pleasing to contemporary ears. The insistence that this was folk rather than art music was part of the West's desperate need for what's "raw", but also the Bulgarian political system's search for what was "authentically Bulgarian".

The arrangements Le MystΦre sang on Thursday were fascinating, that intricate women's harmony (particularly those from the Shope region, close to Sofia), those rhythmic shifts you never see coming, those dissolves into little laughs and whinnies and yelps.

But best of all was the solo voice, surely influenced by Bulgaria's position at the gates of the East, full of extraordinary ornamentation, which unlike that of sean n≤s, is wordless. This was heard particularly in D. Spassov's wonderful delivery of Krassimir Kyurchiysky's song of home-sickness, Give me, O Lord.

The concert was rapturously received, and deservedly so, but it left this writer longing to hear her Bulgarian folk songs neat.