In February 1991, U2 resumed the album’s sessions in the seaside manor “Elsinore” in Dalkey, renting the house for ₤10,000 per month. Lanois’ strategy to record in houses, mansions, or castles was something he believed brought atmosphere to the recordings. Dublin audio services company Big Bear Sound installed a recording studio in the house, with the recording room in a converted garage diagonally beneath the control room. Video cameras and TV monitors were used to monitor the spaces. Within walking distance of Bono’s and The Edge’s homes, the sessions at Elsinore were more relaxed and productive.The band struggled with one particular song—later released as the B-side “Lady With the Spinning Head”—but three separate tracks, “The Fly”, “Ultraviolet (Light My Way)” and “Zoo Station” were derived from it. During the writing of “The Fly”, Bono conceived an alternate persona based on a pair of oversized black sunglasses that he wore to lighten the mood in the studio. Bono developed the character into a leather-clad egomaniac also called “The Fly”, and he assumed this alter ego for the band’s subsequent public appearances and live performances on the Zoo TV Tour.
In April, tapes from the earlier Berlin sessions were leaked and bootlegged. Bono dismissed the leaked demos as “gobbledygook”, and The Edge likened the situation to “being violated”. The leak shook the band’s confidence and soured their collective mood for a few weeks. Staffing logistics led to the band having three engineers at one point, and as a result, they split recording between Elsinore and The Edge’s home studio. Engineer Robbie Adams said the approach raised morale and activity levels: “There was always something different to listen to, always something exciting happening.” To record all of the band’s material and test different arrangements, the engineers utilised a technique they called “fatting”, which allowed them to achieve more than 48 tracks of audio by using a 24-track analogue recording, a DAT machine, and a synchroniser. In the June 1991 issue of U2’s fan magazine Propaganda, Lanois said that he believed some of the in-progress songs would become worldwide hits, despite lyrics and vocal takes being unfinished.
During the Dublin sessions, Eno was sent tapes of the previous two months’ work, which he called a “total disaster”. Joining U2 in the studio, he stripped away what he thought to be excessive overdubbing. The group believes his intervention saved the album. Eno theorised that the band was too close to their music, explaining, “if you know a piece of music terribly well and the mix changes and the bass guitar goes very quiet, you still hear the bass. You’re so accustomed to it being there that you compensate and remake it in your mind.” Eno also assisted them through a crisis point one month before the deadline to finish recording; he recalls that “everything seemed like a mess”, and he insisted the band take a two-week holiday from working on the album. The break gave them a clearer perspective and added decisiveness.
After work at Elsinore finished in July, Eno, Flood, Lanois, and previous U2 producer Steve Lillywhite mixed the tracks at Windmill Lane Studios. Each producer created his own mixes of the songs, and the band either picked the version they preferred or requested that certain aspects of each be combined. Additional recording and mixing continued at a frenetic pace until the 21 September deadline, including last-minute changes to “The Fly” and “One”. The Edge estimates that half of the work for the album sessions was done in the last three weeks to finalise songs. The final night was spent devising a running order for the record. The following day, The Edge travelled to Los Angeles with the album’s tapes for mastering.