[QUOTE=si_blakely]
While U2 do write in major keys, I recall reading an interview with the Edge where he stated that he fairly deliberately avoids using the third (major or minor) in his playing to create a sense of tension and mystery - something slightly unresolved in the music.
Si
[/QUOTE]
That’s fine and all, but that’s nothing special. Rock guitarists have long been avoiding the third with “power chords.” And blues guitarists for even longer.
Almost always, the tonality of a song is implied somewhere in the melody line. It’s awfully difficult to sing a melody and not have the third in there. A noteable exception is blues where the tonality can be ambiguous, at least when analyzing it from a traditional Western music theory perspective.