On the September 28 airing of SBS's Chuseok special program called 'CPR Song,' Red Velvet's Wendy and Jung Joon Il harmonized to a long-forgotten song titled "76-70 = (heart)" by singer Seo Ji Won. 

The song's original composer, Park Seon Ju said in an interview, "I composed and wrote this song and even sang it with [Seo Ji Won]. It's about a man and woman who are in an ambiguous relationship." 

"This song has never been sung on stage before. I hope they will sing it with heart because I believe it will make for a fantastic stage and special memories." Through Wendy and Jung Joon Il's vocals, the judging panel and the audience recollected memories of Seo Ji Won, who passed nearly a decade ago. 

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'CPR Song' is a special program which revolves around a concept of enjoying artists' songs which are considered hidden gems that didn't make the cut as the album's title tracks. 

Check out their wonderful performance above!