SEE ALSO: Hongki talks F.T. Island's military plans, dancing for new solo album, and more at 'DO n DO' release event

In the clip above, Roy Kim reveals the most famous cover song he ever did was Kim Kwang Seok's "Becoming Dust". Upon hearing this information, Kim Jong Kook mentioned he has sung on the remake version and Hongki also had a chance to sing the song during a musical. 

The three decided to collaborate together spontaneously for the audience. The song is considered to be one of the greatest songs in Korean music history and the three absolutely nailed it. They were able to harmonize and work together easily to impress everyone in the studio.

Check out the cover above.