For Song Kang, it is a comeback.
For Lee Jun-young, it is a temporary goodbye.
The two actors meet at a strangely fitting crossroads in tvN’s upcoming youth music drama Four Hands, Two Sonatas, which premieres on August 29 at 9:10 p.m. KST. Song Kang completed his Army service in October 2025, while Lee Jun-young enlisted as an active-duty soldier on July 21, 2026.
That makes the drama both Song Kang’s first post-military series and Lee’s last starring role filmed before enlistment.
At an online press conference on August 25, Song Kang, Lee Jun-young and Jang Gyuri explained just how seriously they approached the music and the decade long relationship at the center of the story.
Two pianists, one piano and completely different kinds of talent
“Four hands” is a classical piano technique in which two musicians sit at the same instrument, with one generally playing the higher register and the other the lower. The drama uses that idea as a metaphor for its two central characters.
Song Kang plays Kang Bi Oh, an elite pianist whose success comes from relentless discipline. He has spent his life winning academically and musically, yet remains driven by a deep need for recognition particularly from his famous conductor grandfather.
Then Choi Jung Yo appears. Played by Lee Jun-young, Jung Yo possesses the kind of instinctive musical talent that threatens everything Bi Oh has built through effort. The two meet at 17, form a powerful musical bond and eventually become rivals. The drama follows them for 10 years, from age 17 to 27, when promotional material suggests the harmony they once shared has turned into something far colder.
That transformation appears to be one of the drama’s central mysteries: what could happen over a decade to turn two young musicians who once played side by side into men who can barely face each other?
Song Kang trained for months to look like a real pianist
For Song Kang, returning to acting also meant learning how not to look like an actor pretending to play piano. He said he began piano lessons several months before filming and repeatedly studied footage of his instructors, paying attention not only to finger movements but also to the small physical habits of experienced performers.
The challenge was not simply hitting the right keys. Bi Oh is someone who has essentially built his entire identity around the piano, so Song wanted the instrument to feel natural around him. At the same time, he said the most important part was preserving Bi Oh’s emotional arc beneath the technically demanding performance scenes.
It is a particularly meaningful role for Song, who was discharged from the military on October 1, 2025 after approximately 18 months of active-duty service.
He admitted that returning to a drama set made him nervous, especially during the first script reading. But working with Lee Jun-young helped. According to Song, Lee responded naturally to whatever he brought into a scene, allowing him to settle back into acting more comfortably.
Lee Jun-young listened to classical music even on his days off
Lee approached the piano differently.
Rather than portraying a lifelong elite student, he plays a character whose natural ability emerges under very different circumstances.
Jung Yo had distanced himself from the piano after painful experiences, only to encounter Bi Oh and find himself drawn back toward music.
To understand that world, Lee said he began listening extensively to classical music even during his days off.
He also worked closely with director Park Hyun-seok, who mapped acting beats to specific moments in the music and, according to Lee, knew the pieces well enough to give direction almost second by second. Lee has described Jung Yo as one of the most emotionally varied characters he has played and said the role was an opportunity to show audiences a different side of his acting range.
Jang Gyuri is the person who hears both geniuses first
The story is not only about the two pianists.
Jang Gyuri plays viola major Hong Jae In, a student with exceptionally sensitive hearing and perfect pitch.
Jae In has known Bi Oh since childhood and can recognize his playing almost immediately. But when she hears Jung Yo, she detects something entirely different and becomes one of the first people to recognize his hidden talent. That places her in a fascinating position between the two.
Jang explained that each man means something different to Jae In: Bi Oh is someone whose dreams she wants to support, while Jung Yo is someone whose possibilities she wants to uncover. As their friendship, ambition and rivalry change over 10 years, her relationship with both men is expected to change as well
Their closest scenes were literally very close
The title also created an unusual filming problem.
Song Kang and Lee Jun-young frequently had to sit together on the same piano bench while performing four-hands pieces.
Song joked that the bench sometimes felt particularly cramped because of Lee’s build. Lee, however, said the physical closeness actually helped them become comfortable with one another faster.
Unlike productions where actors bond through action scenes or heavy dialogue, many of their scenes required them to communicate simply by looking at one another and responding through music.
That intimacy seems crucial to the story.
The rivalry will only matter if viewers first believe these two men genuinely understood each other.
The music is not background it is part of the storytelling
Director Park Hyun-seok said working with classical music required extensive preparation because it was unfamiliar territory for him, but the cast’s work and support from music professionals allowed the production to place meaningful pieces throughout the drama.
The cast repeatedly emphasized the same point during the press conference:
Listen to the drama, not just watch it.
Lee Jun-young suggested approaching the series almost as if listening to and slowly appreciating a classical piece. Song Kang similarly encouraged viewers to pay attention to how the piano, viola and other instruments interact with each character’s emotions.
Four Hands, Two Sonatas premieres August 29 at 9:10 p.m. KST on tvN.