From grandmother to granddaughter, the tradition of Bis'tritsa singing is alive and well in Bulgaria. Recognized by the United Nations as an "intangible cultural heritage of humanity", this form of folklore is thought to date back thousands of years.

These women from the picturesque village of Bistrica in Bulgaria are performing a special ritual for newborn babies, to grant them health and vitality.

From grandmother to granddaughter, the tradition of Bis'tritsa singing is alive and well in Bulgaria.

This annual Midwife Day is called 'Babin Den' in Bulgarian from the word 'baba' which means old woman or grandmother. This is because, in the past, old women were the village midwives and helped the younger ones to give birth.

But aside from breaking bread and burning incense, these women hold a special skill that makes this ceremony particularly magical.

They are part of an all female choir called 'Bistritsa Grannies', and they've helped preserve the authentic sound of folklore melodies with a peculiar polyphonic singing style.

The choir was founded more than half a century ago, and the polyphonic singing, dancing, and specific ritual practices have been passed down over the generations. The songs of the Bistritsa Grannies accompany ritual feasts. There are songs for each rite, for each labour activity, as well as just for entertaining.

82-year-old Krema is the oldest of the Bistritsa Grannies, and she explains how they blend their voices.

She said, "We sing the same song, some do the first voice, others the second and the third one. We sing in three voices, be it in the morning when we go out to the field, or in the evening, on our way home. Some walk and sing coming from one side of the village, others walk singing from the opposite side, and the air above the village is filled with our songs."

A decade ago, the UN cultural agency UNESCO inscribed the Bistritshki Babi as part of the "intangible cultural heritage of humanity".

"In other words, here in Bistritsa we are witnessing a phenomenon of traditional culture demonstrated in a way that makes us scholars believe it has existed for thousands of years," Ph.D Mila Santova, ethnologist.

For the last 20 years or so, the Bistritsa Grannies have been training younger singers to continue the musical heritage. The old singers and a group of young women perform as the "Bistritsa Grannies and Their Granddaughters".

Grannies in Bulgaria keep ancient singing tradition alive

And the repertoire they are handing down - without resorting to notation or recordings - comprises more than 300 songs.

With such efforts, the foothills of Vitosha Mountain shall ever ring with the sound of these wondrous grannies!