It's no secret that Genshin Impact is putting more into their characters than ever before, thanks to the huge success of the game. Yun Jin is one of the most unique characters introduced in the game as she has dual voice actresses voice. One does her normal lines, while the other is there to provide her singing voice.
Yun Jin is a character designed to represent the art of Chinese opera. MiHoYo wanted to breathe new life into this dying art, so they paid a professional opera singer to provide songs for Yun Jin's character. She is voiced by Yang Yang in all languages to show off the artist's incredible vocal range and talent.
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Here is a photo of the artist recording a song for YunJin:
She is popular in the opera circuit, but outside of her home country she is not widely known. MiHoYo hopes that by introducing her singing to Genshin Impact, a wider range of people will come out to support and revitalize Chinese opera. If you want to know more about Yang Yang's performance, you'll have to check out Bilibili.
For more Genshin Impact content, check out How old is Diona in Genshin Impact? on Pro Game Guides.