This song has all KINDS of ostinato going on. Starting from the beginning with the synth playing the arpeggio ostinato, then adding the bass line ostinato, these two parts create a base for the lyrics to build off of. The bass line is quite a popular chord progression: I -> V -> vi -> IV (or Tonic -> Dominant -> Submediant -> Subdominant…see here for explanation on scale degree). You may recognize the bass line (chord progression) from other songs, such as Jason Mraz’s “I’m Yours“; The chorus of Maroon 5’s “She Will Be Loved“; and the Beatles’ “Let it Be“, among many others.
After the first chorus (1:52) yet another ostinato is introduced in the guitar. Unlike the synth which continues through the entire song, and the bass which, for the most part does as well (it drops out for a few measures, then comes back in for the remainder at 4:07), the guitar ostinato comes in and out, starting for the first time at 1:52, then 2:45, 3:25, and finally 4:19.
Sure, there’s also the lyrics and Bono’s voice, but the reason why I love this song is because of the ostinato.