Cheolhyeongeum 철현금 - 鐵絃琴

CHEOLHYEONGEUM, which means “the geomungo with metal strings.”

It is said that master Kim Yeong-cheol created the instrument by remodeling the Hawaiian guitar in the 1940s. (source KBSWORLD RADIO)

At the time, it was usually utilized as an accompaniment to changgeuk performances by traveling theatrical troupes.
Changgeuk or ch'angguk is a traditional Korean opera, performed as a play but in the Korean folk song style known as pansori.