Released in 2005, Park Sang Chul's "Unconditional Love" has become a trot standard and a noraebang go-to that's beloved for its energetic melody and instantly recognizable "cha cha cha" chorus. The song introduced K-pop fans to Park's passionate singing style, which brings an edge to his snappy electro-trot tunes. However, Park's thrilling vocals are best demonstrated on the ballad "Ja-Ok," where he goes from a gentle croon in the verses to a full-on, voice-breaking howl in the chorus.