Taeyeon debuted as a member of the South Korean girl group Girls' Generation in July 2007. Due to the pressure of being the leader[18] of the group, she experienced sleepwalking for a period of time.[19][20] Aside from Girls' Generation's activities, Tae-yeon has also made several solo appearances. In 2008, Tae-yeon released two solo songs, "If" for the KBS2's drama Hong Gil Dong[21] and "Can You Hear Me" for the MBC's Beethoven Virus.[22] The song "If" became popular[23][24] on various online music charts, with Hankyung describing Tae-yeon as having "an exceptional voice and sad tone".[25] While "Can You Hear Me" received the YEPP Popularity Award at the 2008 Golden Disk Awards.[26] In a 2014 interview, Tae-yeon described the latter song as one her most difficult to sing, explaining that the introduction had to be delivered as if someone is talking, rather than singing.[27][28] On the same year, Taeyeon also had a duet titled "7989" with fellow SM artist, Kangta. It was featured on both Girls' Generation's self-titled album Girls' Generation, and Kangta's Eternity. In April 2008, Tae-yeon became a DJ on MBC Radio's program Kangin Taeyeon's Chin Chin Radio alongside fellow SM artist Super Junior's Kangin.[29] After Kangin left the program in April 2009, it was renamed to Taeyeon's Chin Chin Radio, as Tae-yeon became an independent host[30][31][32] and continued on until April 2010. She gained the nickname "DJ Taengoo" while hosting this program.[33]
Kim Tae-yeon at the Asia Song Festival on September 2009.
In January 2009, Taeyeon appeared on the MBC's reality-variety show We Got Married and was featured with comedian Jeong Hyeong-don. They played a couple, portraying what life would be like if they were married. When this news was announced, it caused an uproar among South Korean netizens due to the 11-year age difference between the two.[34] She then participated in the song "S.E.O.U.L." (along with Super Junior and Girls' Generation) as an effort to promote tourism for the city of Seoul in South Korea.[35] In September 2009, Tae-yeon released the song "It's Love", a duet with Sunny for the MBC's drama Heading to the Ground.[36]
From February to August 2010, Tae-yeon became a co-host for the KBS2's idol talk show Win Win alongside 2PM's Wooyoung, Choi Hwa-jung, Kim Shin-young, and Kim Seung-woo.[37][38] On May 7, 2010, she had her musical debut as the main female role in Midnight Sun, which is based on the Japanese novel "Taiyō no uta" by Aya Denkawa.[39][40] The musical was about Kaoru Amane, a 17-year-old girl, who suffers from Xeroderma pigmentosum, which forbids her from going out during daytime. She keeps her hopes up by writing songs and singing every night at a train station; Tae-yeon received good press for her performance.[41] She also learned to play guitar for her performance.[42] When reflecting on her experience, Tae-yeon shared that she found musicals to be difficult, citing that her weak concentration made it hard for her to act and sing at the same time.[43][44] Music-wise, Tae-yeon released a duet song, "Like A Star", with her mentor The One,[45] as well as a solo song, "I Love You", for the SBS's drama Athena: Goddess of War.[46] The former song reached number one on Gaon's digital chart[47] and the latter peaked at number two.[48] In 2011, Tae-yeon had a duet, "Different", with Kim Bum-soo; the song reached number two on this chart as well.[49][50] The two singers met again at a concert two years later for another collaboration "Man and Woman".[51]