As U2 continued to struggle with the song, the tense atmosphere of the recording sessions at Hansa Studios in Berlin took its toll. Producer Daniel Lanois arrived at the studios early one morning before the band to work on ideas he had for the song. When Bono arrived, he began singing and contributing vocal ideas, but this conflicted with what Lanois had in mind for the track. Bono and a frustrated Lanois proceeded to argue intensely for over two hours, worrying sound engineer Joe O'Herlihy that a physical altercation would ensue. Bono looks back on the episode with a sense of humour: "That's why I love Danny so much. He cares about the record he's making as much and more than any band or artist he's working with."