Summer breezes ripple across the eastern edge of the Qinghai-Tibet Plateau, turning the fields and mountains of Minxian county in Dingxi, Gansu province, a vibrant green. As farm work eases, villagers flock to flower-filled meadows, gathering for the region's Hua'er (flower) folk song festival. This year, among the crowds, a familiar figure returns: 69-year-old Dutch ethnomusicologist Frank Kouwenhoven, who records the singers' impassioned voices with quiet intensity.

The oral art form Hua'er, expressed in various dialects, originates from lyrics that compare women to flowers and has been cherished by nine different ethnic groups for hundreds of years. In 2009, UNESCO inscribed it on the Representative List of the Intangible Cultural Heritage of Humanity.