Korean flutes are generally made of bamboo, but occasionally of semi-precious stone such as jade. They are either vertical or horizontal types. This piece is played on a horizontal flute. There is a legend about the Royal Flute called Man Pa Sik, which says that when the king played it all the waves of the sea became calm. The actual composer of this piece is unknown, though it was popularized by Pahk Yun, a scholar in the 15th century era of King Sejong. You can hear the pak (wooden clapper) that marks the beginning and the end of the piece.
Man Pa Sik - Ah Ahk (Ten Thousand Waves Calm)