The 23-year-old star, who was chosen to sing the theme for the latest Bond movie, finds the track hard work to perform as the high notes are too difficult for him, reported Female First.
"I've only actually sang the song once really. I did the demo in the studio, and they used it. It's horrible to sing. Horrible. I almost regret -- no, I don't regret... It's just so high," he said.
The "Stay With Me" hitmaker attended the world premiere of "Spectre" at London's Royal Albert Hall on October 26.