A blurb in Rolling Stone suggests that U2 are going to perform "rarities that the band is excited to be playing live for the first time". You can check out the full piece in this tweet—it is short, and also mentions longer sets and augmented reality. What could those rarities be? Let's have a look.

First, however, a caveat. It is possible that this comment is somewhat hyperbolic and the rarities will be songs that have been performed live before, but infrequently or not for a long time. U2 have, after all, recently posted a clip of them rehearsing Who's Gonna Ride Your Wild Horses, which has been played 79 times in full, but just 16 times since it disappeared from the ZooTV setlist during 1992—five times electric and eleven times acoustic, all on the Vertigo Tour in 2005–06. Nonetheless, let's take the Rolling Stone report at face value. If U2 play rarities that have never before been performed, what could they be?

The tone of the report suggests this is not meant to cover songs from Songs of Experience, for it mentions new songs separately. We already have a FAQ about album songs never performed live. To summarise it, the following album songs (listed chronologically) await a live debut:

• Stranger in a Strange Land
• Is That All?
• Drowning Man
• The Refugee
• Red Light
• Promenade
• 4th of July
• Elvis Presley and America
• Heartland
• Acrobat
• Some Days Are Better Than Others
• Playboy Mansion
• When I Look at the World
• Grace
• One Step Closer
• Stand Up Comedy
• Fez-Being Born
• White As Snow
• Cedars of Lebanon
• Sleep Like a Baby Tonight
• This Is Where You Can Reach Me Now

It strikes me that the most realistic options from this list are Drowning Man, Acrobat, and Reach Me Now. Drowning Man was rehearsed extensively during 2009 on the 360 Tour, with many fans anticipating it would debut live at the third Dublin show (White As Snow was also suggested for this show, according to Willie Williams). Bono also snippeted Drowning Man at the end of One during some shows last year, so it evidently remains on his mind. Acrobat was rehearsed in August 1992 before the third leg of ZooTV, it is a long-standing fan favourite, and the 30th anniversary of Achtung Baby is not far away. Reach Me Now provides a link back to Songs of Experience's companion album. All three songs are well suited to the live arena, not difficult to play, and would be likely to engage audience members unfamiliar with them. Personally, I would love Heartland, which is one of my top three U2 songs, but dreams are free and it seems an unlikely candidate.

Perhaps my idea of realistic is inaccurate, though. U2 have rehearsed both Playboy Mansion and One Step Closer recently—see the setlist for the rehearsal of 27 April 2015 in this article. Are either of these songs still on the band's radar? You can listen to them working on Bullet the Blue Sky into One Step Closer during the 2015 rehearsals here.

What about b-sides, non-album singles, and other rare U2 songs? It's easier to list those that have been played. Popular b-sides such as The Three Sunrises, Love Comes Tumbling, Boomerang II, Luminous Times (Hold on to Love), Walk to the Water, Lady With the Spinning Head, and Summer Rain, to name a few, have never appeared live. Bono snippeted Walk to the Water in November last year; could it be on his mind? I would like to cast a vote for Wild Irish Rose, a song never released but used in a documentary (despite common misconception, it is not a cover of the traditional song of a similar name), a second vote for Bono's finest stream of consciousness, Treasure (Whatever Happened to Pete the Chop?), and, of course, a third vote for the song responsible for the greatest U2 TV moment ever, the one and only Womanfish.

The limited number of songs U2 have never played before live that would be effective in arena-sized venues leads me to suspect that the "rarities... play[ed] live for the first time" comment might be overstating it. Perhaps we will get one or two live debuts. But hopefully we will see the resurrection of songs that have not received their due. If they want to celebrate the 35th anniversary of War, as some rumours have suggested, a fine candidate is Like a Song, played just once, while Seconds and Surrender have not graced the stage since 1985. And if they throw Pop a coming-of-age 21st birthday party, Mofo, not played since 1998, and Gone, not played since 2001, are total bangers that feature in many lists of fan requests, while under-rated gem Do You Feel Loved never got a fair chance with just six performances to its name.

Whatever the case, the Rolling Stone report is more than enough to get fans excited. Let's just hope the prospect of longer setlists and rarities does not go the way of the promised but never delivered "pair of setlists" alluded to in the original announcement of the 2015 tour.