“Welcome” is a song that was developed for the album No Line on the Horizon.
Daniel Lanois talks about this song in his book, Soul Mining. In the book, published in 2010, Daniel Lanois is looking back at work with U2 on the album in 2008:
“Welcome” is a big part of this U2 record. Open the door and let the listener into the huddle. Believe in what you’re doing and they will believe in you. This song is made up of two Larry Mullen drumbeats—one loop, one played—trance-bass relentless; the Edge conducts the chord changes, with me and Eno floating on top, and a nice spitting lyric from Bono, with a catchy yodel, a slight Germanic flavor, a distant relative to “Beautiful Day.” My head is still swimming from the delivery of a full lyric by the man himself, while the Edge sang his harmony. This is the kind of rock song I want to listen to.
The song has not appeared by name since, and it may have developed into another song over time.