C'est si bon (Korean: 쎄시봉; RR: Ssesibong) is a 2015 South Korean musical drama film written and directed by Kim Hyun-seok. It was released on February 5, 2015. C'est si bon (French for "It's so good") was a legendary, real-life acoustic music lounge in the 1970s located in Mugyo-dong, Seoul. It was very popular with Koreans in their twenties and thirties, who went there to listen to live music performed by some of the most talented young musicians of the era. Among them was the folk music duo Twin Folio composed of Yoon Hyung-joo and Song Chang-sik; this film depicts the band's beginnings while including a fictional third member, Oh Geun-tae.