Aborted sessions with Rick Rubin In 2006, U2 started work on the follow-up to
How to Dismantle an Atomic Bomb (2004), collaborating with producer
Rick Rubin. After U2 guitarist
the Edge worked individually with Rubin in Los Angeles, the group spent two weeks in September 2006 completing songs with the producer at
Abbey Road Studios in London. Later that year, the band released two songs from these sessions on the compilation album
U218 Singles: a cover of the
Skids' "
The Saints Are Coming" with
Green Day, and "
Window in the Skies". Rubin encouraged a "back to basics" approach and wanted the group to bring finished songs to the studio. This approach conflicted with U2's freeform recording style, by which they improvised material in the studio. Bassist
Adam Clayton said: "once we have a song, we're interested in the atmospherics and the tones and the
overdubs and the different stuff you can do with it... things that Rick was not in the slightest bit interested in. He was interested in getting it from embryonic stage to a song that could be mixed and put on a record."
Sessions with Brian Eno, Daniel Lanois, and Steve Lillywhite similar to the one pictured. U2 subsequently began working with
Brian Eno and
Daniel Lanois in May 2007. Bono, who had accepted an invitation to the
World Sacred Music Festival in
Fez, Morocco, invited his bandmates to attend. Bono also invited Eno and Lanois, hoping they would collaborate with the band as full songwriting partners in recording an album of "futuristic spirituals" or "future hymns"—songs that would be played forever. Recording during the festival exposed the group to
Hindu and
Jewish music,
Sufi singing and
Joujouka drums. The exotic influences inspired them to pursue a more experimental sound. Clayton said the music they heard in Fez "had a primitivism ... but there was an other-worldly feel, there was that connection with that Arabic scale." The band described many of the tracks conceived in these sessions as unsuitable for radio airplay or for playing live. The songs "
Moment of Surrender", "
White as Snow", "
No Line on the Horizon" and "Unknown Caller" were written at this time; each track was recorded in one take.
Steve Lillywhite was brought in to produce a few tracks during these subsequent sessions. In pre-release interviews, U2 compared the extent of their expected shift in musical style to that of
Achtung Baby. The band scaled back these experimental pursuits, however; Mullen noted: "at a certain stage, reality hits, and you go, 'What are we gonna do with this stuff?' Are we going to release this sort of meandering experimentation, or are we gonna knock some songs out of this?" Clayton filmed the band's progress during the album's production; these videos were added to the subscribers' section of U2.com. On 16 August 2008, an eavesdropping fan recorded several songs playing from Bono's beach house in
Èze, France. These "beach clips" were uploaded to
YouTube, but removed at
Universal Music's request. In November 2008, the Edge confirmed the album's working title as
No Line on the Horizon and noted that the band had to move quickly to complete
mixing to meet the new February release date. In an interview with
Q, the group revealed that rapper
will.i.am had worked with them on the track "
I'll Go Crazy If I Don't Go Crazy Tonight". In December 2008, U2 recorded at Olympic Studios in London, putting the finishing touches to the album The band struggled to complete "
Stand Up Comedy", a song they had been working on since the Fez sessions 16 months previously. The song had been through multiple iterations and titles, including "For Your Love" and "Stand Up". "Winter" appears in the accompanying
Anton Corbijn film
Linear and the 2009 war film
Brothers. The band changed many of the tracks' names during recording, retitling "French Disco" to "
Magnificent" and "Crazy Tonight" to "I'll Go Crazy If I Don't Go Crazy Tonight". "Chromium Chords" became "Tripoli", and finally "
Fez – Being Born". The band considered "Fez – Being Born" and "Get On Your Boots" as album openers, but ultimately decided on "No Line on the Horizon". At the end of the sessions, the band chose to include "White as Snow", a quiet song about a dying soldier in Afghanistan, to balance out the earlier, rockier tunes.
Follow-up album 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". 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. == Composition ==