Mullen, who had mostly been absent from the sessions to start a family and nurse a worsening back injury, had major surgery on his back in November 1995. Mullen was unable to drum properly during this period, forcing U2 to abandon their usual methods of songwriting as a group but also allowing them to pursue different musical influences. Mullen admits that he was upset that the band entered the studio without him, cognizant that key decisions would be made in the early months of recording. Eno attempted to convince the other band members to wait for Mullen, but as the Edge explains, "The thinking was that we were going to further experiment with the notion of what a band was all about and find new ways to write songs, accepting the influence, and aesthetics of dance music... we thought, 'Let's just start with Howie mixing drum beats and see where that gets us.'" Mullen was back in the studio three weeks after his surgery, but his back prevented him from fully dedicating himself to recording. As he described, "I needed a little more time to recover. But we were struggling with some of the material and for the project to move ahead, I had to put a lot of time in." Sessions ceased temporarily in January 1996 to allow Mullen to rehabilitate.