As the BBC reports, Katy Perry was among those addressing the deadly attack when she took to the stage for an intimate performance at London's Water Rats Pub last night. (Other singers paying tribute to Manchester include Miley Cyrus during her Voice performance, Harry Styles in Mexico, and Céline Dion, who called on her Vegas fans to stand and hold hands as a show of solidarity.)
Perry choked back tears as she spoke to concert-goers.
"This week has been really hard," the "Chained to the Rhythm" singer said. "It sucked. It was hard for you guys, I know that. It was hard for me because we all love music. We all listen to the same music. And you think about it and think, That's my friend, that's my sister, that's my cousin, that's my brother, that's the person that loves music.
"It's awful," she repeated. "It's awful. It's awful. And whatever you can do to help, you should. And if you can't do anything that's fine. But what you should do is not let them win."
The crowd broke into applause, as Perry prepared to belt out her 2012 single "Part of Me." The power-pop song is about becoming empowered after heartbreak.
"I'm going to sing this next song for them," she told the audience. "They can never take that part for us ever. Ever."
She then called for a moment of silence to honour those affected by the attack.
Watch footage of the emotional moment below.