My oh my, does everything have to be so doom and gloom, U2girl?
My take is this:
Bono's vocals have been different on *every* U2 album to date. Some of this is a result of maturation; some of this is a result of deterioration -- but much of it is a result of adaptation, I'd say.
Album to album:
Boy: a very young Bono just balancing on the tight rope, and doing a grand job of it. His voice would teeter, but he would have much to learn, and that he would learn. Here he sounds as though the whole world is singing along, and so he should. There's a lot to celebrate on Boy, and on this record Bono's voice is full of celebration and a kind of knowing that the next step is inevitable to the first. He's willing to walk that tight rope, and even do it blindfolded if it will get him there, and it does.
October: On songs like the title track, you can hear, for perhaps the first time, the Bonoism trademarks coming through. The slightly breathy, almost speaking quality, followed by a spiritual burst "you go ooooon..."
War: Bono developes his careening wail, and begins to command his audience with a fervent relentlessness. The high end is not totally mastered, but he's able to reach notes and sustain in a manner he was never able to. This is when the screams begin to keep up with the melody lines and hooks. Many would say this was the end of the era when Bono's voice was a "one trick pony" -- when he only was able to throw in the money shot, high octane punches, without really being able to sing very well, technically.
The Unfogettable Fire: After taking some voice lessons, Bono has entered stage 2 of his vocal growth. He now is able to hit higher notes than ever before, and sustain them. This is perhaps the first time when we begin to hear the "U2 sound": the sound of guitar, drums, bass and vocals coming together into one sound -- and somehow expanding out from itself. Songs like 'Pride' and 'Bad' exemplify this, and vocally Bono has found an ability to reach the listener in a manner never before. This is perhaps the first time that the magic of U2 forms as an obvious sound -- and it is the vocal delivery that begs that sound to form.
The Joshua Tree: We hear a much more refined vocal delivery, one where the ecstatic heights of The Unforgettable Fire are delivered in a controlled manner, a much more focussed manner. On songs like 'With or Without You' and 'Red Hill Mining Town' it becomes clear that U2 aren't a band that we can all sing along to as easily anymore. There is something mystical, almost other-worldly going on on these songs. Bono's falsetto has a different quality to it, as well, as it sounds as though it has travelled for miles and miles through the forests and dense atmospheres of the album. It sounds almost like the wind in places, like the anguish of human frailty and suffering in other places. Bono's voice has become an organic instrument of the elements -- and the result of us crashing into those elements -- on JT.
Rattle and Hum: Here, Bono has lost the high end of The Unforgettable Fire for a deeper, richer, more penetrating vocal. There is a "strongness" about his voice that gives the impression that this singer has grown up, almost too fast. On songs such as 'Angel of Harlem' his voice is now able to dance, climb up walls and down ladders (in much the same way as he himself used to do at concerts in the early days!). He has become somewhat of an acrobat (and no, not to talk like this and act like that) vocally, and we can hear a new "golden" quality to his voice. This appears in his falsetto as well -- but more so during the Lovetown Tour, which can almost be a "vocal era" unto itself. It is during this tour that Bono really masters his falsetto, and becomes almost rock's version of an opera singer (not leaving Freddie Mercury alone for a minute). It's the sound of a singer reaching for the light with his voice alone. This era of Bono's voice is a very short, but very sweet one, and flows very quickly into the next stage...
Achtung Baby: The voice has become more subtle, more "throaty" and slightly more reserved. Bono can still belt it out when he wants to ('One' & 'Wild Horses', etc), but he's relying more on his ability to use intonation and phrasing to get convey the emotion. His "smokey" voice is at its all time peak here, and it works perfectly for the subject matter of Achtung Baby. He works the cracking ability, which he just started to develop during R&H, to perfection, and the result is the sound of the early part of stage 3 of his vocal growth -- with the feeling that he could, at any time, kick it into 5th gear again.
Zooropa: Bono chooses to use the reserved model developed during Achtung Baby, but takes it to the next level. No longer do we hear any wide open vocals that are still found on parts of Achtung Baby and that run rampent on Joshua Tree and Rattle and Hum. The voice is now used in a slightly different pitch, and the falsetto is brought to the forefront. The phrasing and intonation are what carries the vocals throughout, and the raspiness is now part of what defines Bono's style, which wasn't really the case before.
Pop: A very relaxed vocal, relying heavily on a higher pitch. The richness has completely gone, and is replaced by a rougher, dirtier sound. There is more of a cascading quality to the vocals, a kind of shimmering in and out of falsetto (ie, 'Playboy Mansion' and 'Discoteque'), with a very smooth transition between falsetto and normal singing. The line has become blurred in this sense, and we only wonder what Bono will do next...
All That You Can't Leave Behind: There are many similar stylings to that of Pop, but this time there is more emphasis on, in terms of material, melody. However, the change in material brings out an honesty in the vocal delivery that hasn't been heard ever before. The roughness of Bono's voice only accentuates the meaning and credibility of the songs. There is a new found soul in this vocal delivery that is different from the one found on R&H. It is a soaring style, but not so high that we, the listeners, can't sing along. In this sense, the vocals are very ordinary, but it's a very beautiful ordinary. The vocals for 'Beautiful Day' for, example, sound so ordinary at times that it could be anyone -- but there is always a shimmer of something extroardinary coating them. The "See the world in green and blue..." segment really exemplifies this. It comes out of nowhere, and I picture Bono, standing there at the mike, coming up with this while sharing a martini with God. It's this combination of earthiness, perhaps mortality, with a higher agenda, that really transcends his vocal delivery on this album.
What I find really interesting about all these different vocal styles, is that even though they are so different, they are instantly recognizable as Bono. Even on ATYCLB, where Bono sings in a completely new pitch ('Beatiful Day' for example), he still sounds "totally Bono". It's something really undescribable.
I don't really know if ATYCLB is the end of stage 3 or the beginning of stage 4, but time should tell. Bono has said that ATYCLB was either going to be the end of U2, or the beginning of something else. Make of that what you will...
But to answer your question, U2girl, I think Bono will follow in much the same vein as, say, Leonard Cohen. He will simply adapt his vocal style -- like he has always done -- to fit the mood, the material, his own abilities and directions as a singer. I don't think Bono will ever compromise the music U2 makes simply so that he'll be able to sing a certain song for another 10 years, or whatever. If that were the case, they wouldn't have played 'Bad' or WOWY or even 'Pride' last tour. I think these songs will morph into something that he will always be able to perform, as long as U2 is alive.