Along with more stunning teaser images, SM Entertainment revealed the Girls' Generation member to feature in Taeyeon's upcoming solo album 'Why'!

The label announced that Hyoyeon showed off her powerful rap skills in a track titled "Up & Down"! The fellow Girls' Generation member's support added even more excitement to Taeyeon's new upbeat song.  

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Meanwhile, Taeyeon's 2nd mini album is set for release on June 28!