It was actually a last-minute decision.

Samjiyon Orchestra, a renowned art troupe of North Korea, held its concert on February 11 in Seoul, South Korea.
Seohyun from girl group Girls' Generation joined the finale of the concert and sang 'Let's Meet Again' and 'Our Wish is Unification' together with the troupe's performers.

▶ [SBS Star] VIDEO: Seohyun Performs with the North Korean Art Troupe

On February 12, a source from Seohyun's side explained that Seohyun decided to join the concert after receiving a request from the Blue House on the day of the concert.
The source stated, "It wasn't something that Seohyun prepared for in advance. She joined the concert after she received the sudden request. The Blue House asked for her appearance, without saying much explanation else other than 'We really hope you would join the concert'. Seohyun did not even have time for a rehearsal, as it was such a sudden decision."
Kwon Hyuk-ki, director of the Blue House's Chunchugwan(the Presidential Press Center) also explained why they selected Seohyun.

He said, "All the vocalists of the troupe were females, and we didn't have enough time to rearrange the song for a male singer to perform together. As the concert had many elderly audience, we searched for a singer with general public's popularity. While we were looking for an artist who could practice in the short amount of time, Seohyun gladly accepted our request."

The director continued, "At first, the North Korean troupe opposed the joint performance due to the (lack of) time to practice, but we persuaded them to put the joint performance on stage."

(Credit= Yonhap News Agency)

(SBS Star)