For his role, actor Yoo Ji-tae practiced singing everyday for more than a year and underwent further vocal training to acquire the technique to believably lip sync every opera song he sings in the film; he also took English lessons.
The film's early working title was Miracle, but director Sang-man Kim changed it because he thought it disclosed the ending, while he hoped the unfamiliar term lirico spinto would arouse Korean viewers' curiosity. Lirico spinto, or "pushed lyric" in Italian, refers to a tenor voice that is versatile enough to sing in the style of a lirico, a singer with a softer voice and a spinto, one with dramatic voice; Bae could do both.
Due to budget constraints, it took six years for the film to be completed. The production crew filmed in Korea, Japan and Serbia for 18 months.