Way before guitars and violins were introduced to Korea, Korean music was dominated by traditional Korean stringed instruments such as these:

A Gayageum (가야금) is a twelve stringed instrument made of wood.

A Geomungo (거문고) is a six stringed instrument plucked with a bamboo stick.

http://www.youtube.com/watch?v=Lc0Y4LkgvEA

A Haegum (해금) is like a two stringed fiddle played vertically with a bow.