The nagak (also called na, sora, or godong)^[1] is a wind-instrument made from a large seashell and played as a horn in Korean traditional music. It produces only a single tone and is used primarily in the military procession music called daechwita. The mouthpiece of the nagak is made by making a hole in the pointed end of the conch,^[2] into which a mouthpiece is fitted.^[1] This instrument is first recorded as being used in Goryeo.^[3]

The shell used is that of a very large sea snail, Charonia tritonis, sometimes known as "Triton's trumpet".^{[citation needed]} This shell is also used as a musical instrument in several other nations.^{[citation needed]}

• Conch (musical instrument)
• Horagai, a similar shell horn used in Japan
• Traditional music of Korea
• Shankha
• Traditional Korean musical instruments