A British singing teacher has said that he was “gobsmacked” when Billie Eilish duetted with his TikTok tutorial to one of her songs.

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Sheridan Coldstream, who is from Buckinghamshire, posted a video on TikTok of himself playing piano and providing singing instructions for Eilish’s song ‘Listen Before I Go’ to help clients on his Total Vocal programme.

Last month, Eilish recorded herself singing the song, which is taken from her debut 2019 album ‘When We All Fall Asleep, Where Do We Go?‘, alongside Coldstream’s piano accompaniment and instructions. The clip has since had more than 32million views and 6.5million likes.

Coldstream told BBC News that it was “completely astounding” that not only was Eilish singing to his piano playing but she was also following his directions.

@billieeilish

#duet with @sheridan_coldstream

♬ original sound – Sheridan

“There’s a bit in the song where she normally goes down,” said the 58-year-old, who runs Total Vocal at his studio. “I suggested that some singers may want to take it higher and she did exactly that, so I was gobsmacked.

“It was immensely exciting and I found the whole thing very moving, it made me tear up several times.”

Coldstream added that he started posting on TikTok in May after a pupil of his suggested that he get an account. Now, he has more than 163,000 followers.

Meanwhile, Eilish recently played a surprise, acoustic set at a record store in the US to mark the one-year anniversary of the release of her second album ‘Happier Than Ever’.

Eilish was accompanied by her brother Finneas and performed four songs during the set at Amoeba Music in Hollywood. Watch a clip here.