Originally sung in exchange between mandarin families, its popularity spread throughout the northern region, and is today one of the most important types of Vietnamese folk song. Men and women take turns singing in a kind of challenge and response to eachother. The songs are generally upbeat, extolling the joys of nature, hard work that is shared by group singing. Melodious, graceful and poetic, the songs are accompanied by dan-bau (monochord), sao-truc (bamboo flute) tam thap luc (dulcimer) with occasional guitar and keyboards. And UNESCO recognized Quan Ho as a Heritage of Humanity on 30 septemper 2009