or a little bit too low". Consequently, the only melody he felt comfortable singing was conversational. Reading poetry by John Keats, Percy Bysshe Shelley, and George Gordon Byron inspired Bono to touch on the theme of temptation in his lyrics. U2 and their production team expended considerable effort to finalise the song. The band added various overdubs during the recording sessions, including percussion loops by Mullen, as well as a sweeping guitar sound created by their engineer Flood that sounded like it went "between the speakers". Producer Daniel Lanois provided additional percussion, playing congas heard during the song's introduction. At one point, assisting producer Brian Eno believed the additions had negatively impacted the track. Eno, who would occasionally visit the studio and review material for a short amount of time before leaving, believed his distance from the album allowed him to provide a fresh perspective. He explained his assistance: "I'd go in and say, 'The song has gone, whatever it is you liked about this song is not there anymore. Sometimes, for example, the song would have disappeared under layers of overdubs." Eno aided the group in removing some of these overdubs. Composition and theme According to Hal Leonard Corporation's sheet music published at Musicnotes.com, "Until the End of the World" is played at a tempo of 101 beats per minute in a 4/4 time signature. The basic key is E major. David Werther, a faculty associate in Philosophy at the University of Wisconsin–Madison, compared "Until the End of the World" with U2's 1987 song "Exit" in an examination of the role music can play in catharsis. He noted that both were powerful songs, but that while "Until the End of the World" allowed the possibility of purification, which he described as the cleansing of the soul "through pity and fear", by placing the listener in the position of Judas Iscariot, "Exit" was an example of purgation, a freeing from excess pity and fear. Werther noted "'Exit' evokes feelings of fear, fear of losing control, giving into one's dark side, perhaps even taking one's life", contrasting it to the "waves of regret" experienced by Judas. Reception Upon the release of Achtung Baby, many critics praised "Until the End of the World". Steve Morse of The Boston Globe thought it was the best song on the album, calling it a "raging rocker" with "fiery bass runs" by Clayton. Morse interpreted some