Task: Question Answering
Input (English): Passage: In February 2009, Bono stated that by the end of the year, U2 would release an album consisting of unused material from the No Line on the Horizon sessions. Bono labelled it "a more meditative album on the theme of pilgrimage". Provisionally titled Songs of Ascent, it would be a sister release to No Line on the Horizon, similar to Zooropa's relationship to Achtung Baby. In June 2009, Bono said that although nine tracks had been completed, the album would only be released if its quality surpassed that of No Line on the Horizon. A December 2009 report stated that U2 had been working in the studio with the goal of a mid-2010 release. The band revealed that the first single was intended to be "Every Breaking Wave".Over time, the album continued to be delayed. In April 2010, U2's manager Paul McGuinness confirmed that the album would not be finished by June, but indicated that a release "before the end of the year [was] increasingly likely." In October 2010, Bono stated that their new album would be produced by Danger Mouse, and that 12 songs had been completed. He also noted that U2 were working on a potential album of club music in the spirit of "U2's remixes in the 1990s". Around the same time, McGuinness said the album was slated for an early 2011 release. In February 2011, he said that the album was almost complete and had a tentative release date of May 2011, although he noted that Songs of Ascent was no longer the likely title. The Songs of Ascent project ultimately did not come to fruition and has not been released; its evolution and apparent abandonment are examined in the book The Greatest Albums You'll Never Hear. Clayton said, "We thought there was more material left over from No Line... we now feel a long way from that material."After numerous delays, U2 digitally released their thirteenth album, Songs of Innocence, on 9 September 2014 in a surprise release. The band appeared the same day at an Apple Inc. product launch event to announce the album and reveal it was being released to all iTunes Store customers at no cost.In October 2014, Bono said that Songs of Ascent "will come" and that the group views it as the third release in a possible trilogy of albums. 
Question: What was the name of the band that released Achtung Baby?
Output (English): U2.