Seoul, Nov. 18 -- Korean traditional music, or gugak, has many faces. Even within its vocal traditions, it can be broadly divided into three regional lineages: Gyeonggi minyo from the central provinces, Seodo minyo from the North, and the narrative art of pansori mainly from The breakthrough came sooner than expected. On Jan. 9, Song uploaded a self-written and unreleased track, "Not a Dream," to YouTube. It soon became a phenomenon: critics called it "an event," as the video amassed over 8.7 million views by late February, doubling in just a few weeks. As of Wednesday, it has surpassed 17 million views.

"While traces of traditional Korean music are naturally embedded in her phrasing and tone, such as the delicate control of 'sigimsae,' ...