This is a rather mature song, so I would be lying if I said I didn’t have my doubts, but she blew me away.I was moved to tears listening to her singing." Following Taeyeon's working relationship with him from the drama Beethoven Virus (2008), musical director Lee Pil-ho was determined to collaborate with her again on his MBC's melodrama The King 2 Hearts (2012) soundtrack, by having her record the main theme song "Missing You Like Crazy".In a 2011 interview, he described Taeyeon as a "smart" student, someone "unlike others who came to him with dreams of becoming a celebrity...[she] wanted to be a singer and reach the top with her own talents." In 2004, he "wanted to acknowledge Taeyeon’s potential" by giving her the chance to be in his song "You Bring Me Joy"."We met so so we decided to go for a walk in town to buy a drink.But I guess, someone saw him and eventually these articles appeared. Yes we met only two of us, but we're just friends, "explicitly denied the rumors that exist.In July 2013, Taeyeon was invited to record the theme song "Bye" for the movie Mr.Go soundtrack, after its musical director was left with a "deep impression" having heard her cover version of a song during a radio appearance.
"Taecyeon just a friend," said Jessica commented on the issue.
It peaked at number two on South Korea's Gaon Album Chart and its title track sold over one million digital copies.
Her second extended play, Why (2016), charted at number one and yielded two Gaon Digital Chart top-ten singles "Starlight" and "Why".
That same year, she won first place at the SM Youth Best Competition and officially received a contract from SM Entertainment.
The training process was so tough that it nearly made her quit at one point; she continued, however, and debuted as a member of girl group Girls’ Generation in August 2007.