To fully understand just how this song has changed since its inception (as we know it, at any rate), I actually went through and analyzed 3 versions of the song (well, technically 6) -- the original recorded version, as well as the stripped down version on JennaWN's channel (technically, it's actually inverted, rather than stripped -- so the loudest tracked parts are actually the quietest ones on the real recording, and vice-versa); the GMA performance on 2/12/09 -- right before the tour officially began; and the most recent incarnation. For this latter version I actually looked at 3 performances -- the one in Galveston, TX, on 7/7/09, the one in Bethlehem, PA on 8/3/09 (which I saw live as well), and the MOST recent one I could find as of this writing, at the Ohio State Fair, on 8/8/09. I looked at all three of these because the first was, in fact, one of the better audio versions of the song (and thanks to whomever recommended it); the second, as I said, more recent, and I actually heard it live, so I could pull on memory to supplement any deficiencies in the recordings; and the last to confirm that no further tweaks have been made to the song. What follows are my notes on all 3 (6?) versions, as well as comments on the significant differences between the three. I should also mention that percussion and telling the difference in the number of guitars used are NOT my strong suits. If anyone wants to supplement or correct what I have below, please, please do.

To make things simple, I just want to clarify the structure of the song as well as any shorthand I'm using:
Intro, Verse 1 (V1), V2, Chorus 1 (C1), Interlude 1, V3, C2, Interlude 2, Bridge, Interlude 3, C3a (all right/night), C3b (okay/day), Outro.

Part I: The recording
Intro: The intro is the melodic riff -- "dum, da da da dum." It's accompanied by light percussion, and played on either 2 or 3 guitars, but the dynamics -- i.e., volume -- indicate it be played fairly quietly (piano).
V1: Here the vocal is accompanied by backup singing (in this case, David himself) with a harmony sung above the melody. V1 also includes guitars, bass, and light percussion.
V2: In V2, however, the percussion kicks in more strongly, and the dynamics change and get a bit louder (forte, probably).
C1: From the perspective of backup vocals, instrumentation & dynamics, nothing changes in the chorus.
Interlude 1: The musical interlude is 8 measures long, sans vocal, with the exception of a "lie, lie, lie" refrain in the latter half of the interlude.
V3, C2: V3 is also played in the same manner, as is C2.
Interlude 2: Then, before the bridge, there is -- I wouldn't say an interlude, per se, but there are four bars of just intrumentation before the bridge kicks in -- and what's interesting from a melodic perspective is that these 4 bars play a melodic refrain that is, while transposed, the same 3-2-4-3 (that would be me-re-fa-me in less obscure terms) refrain as the "whoa-whoa" ending of ADAM.
Bridge: It really is the preceding refrain that helps the bridge pack the punch it has, because otherwise, again -- no noticable difference in backups, instrumentation, or dynamics, except that the final "stay," while still sung in full chest voice, is lower in volume. In this case, that's production at work, not actual vocals, though -- to my ears, anyway.
Interlude 3: Nonexistant. Bridge goes straight into C3a.
C3a, C3b: C3a is actually done a little differently. The instrumentation is layered in over time -- the first line is done much like V1 -- vocal, guitars, bass; the second line brings in the percussion & backup vocals; the 3rd line adds more guitars, or possibly just gets louder and remains that way through the rest of the chorus and through C3b.
Outro: Finally, the outro is played not melodically, but rather rhythmically, as particular chords.

Part II: Lie live, at the start of the tour (from the GMA performance on 2/12/09)
Intro: The intro is done on guitar, but rhythmically -- I think it's on 2 guitars. There's no percussion, no backup vocals -- it's much more stripped down than the recording.
V1, V2, C1: These are all played in the same stripped-down manner.
Interlude 1: The musical interlude is 16 measures long this time (i.e., twice as long), with the melodic refrain that opens the recorded version coming in halfway (8 measures in). The percussion also kicks in at this point, and the song also goes from piano to forte.
V3: V3 continues in this vein, perhaps increasing the dynamics.
C2: The song builds further here, where Andy comes in singing backup harmony for the first 3/4 of the chorus; the instrumentation, however, remains the same. The final line in the chorus, however, is sung without backup vocals, but the instrumentation seems to get louder still, leading directly into the bridge.
Interlude 2: The 4-bar 3-2-4-3 refrain is still there, but David holds that final "lie" from the preceding chorus over it, so there's no real break between C2 and the bridge.
Bridge: This also features all available instruments, only David on vocals, and guitars that are mainly played rhythmically. In this case, the final "stay" is sung in falsetto to move the dynamic down to piano again.
Interlude 3: There is then a (new) 8-measure interlude played on rhythm guitar, with little percussion -- it's still done in piano (the dynamic, not the instrument) and is similar to the stripped down style of the first part of the song.
C3a: This chorus also layers in the instrumentation. The first line is stripped down, and done with vocal, 2 guitars, bass; line two brings in percussion and heavier rhythm guitar; and line three adds backup vocals via Andy.
C3b: Continues the instrumentation (& backup singing?) found at the end of C3a, with some stronger percussion. He ends with some vocal acrobatics on the word "eye" and slows down on the final "lie" to a quieter ending.
Outro: The outro is actually played with the melodic refrain, not rhythmically.

Part III: Lie live, 2nd leg of the tour:
from Galveston, TX, 7/7/09; from Bethlehem, PA, 8/3/09; and from the Ohio State Fair, 8/8/09

Intro: The intro is now back to the melodic version.
V1, V2: Also stripped down, done on just the 2 guitars, with David on vocals
C1: No instrumentation. At all. Done purely a cappella, away from the mic. As stripped down as it is possible to ever get a song.
Interlude 1: All instruments come in at this point -- guitars, bass, percussion -- creating that much more dramatic a change in dynamics & instrumentation; this interlude is also 16 measures long, and the melodic refrain comes in halfway as well; the percussion also comes in more at this point.
V3: Same instrumentation as the interlude, but perhaps a little louder, with David on vocals.
C2: Andy comes in on backups here until "and lie, lie, lie."
Interlude 2: David holds that last "lie" for 2 measures, so half of this section is sort of held over from C2, and half is just instrumental. Same 3-2-4-3 refrain that carries into the bridge.
Bridge: Contains same vocals and instrumentation, with a final "stay" done in falsetto that leads into quieter dynamics.
Interlude 3: 8 measures of just 2 guitars, done rhythmically at first until the 2nd guitar comes in melodically. Retains the quiet dynamics.
C3a, C3b: The first line is a cappella again, but on the mic; the 2nd line has heavy percussion & brings the percussion & bass & rhythm guitar back; the 3rd line brings in the other guitars, and "and look me in the eye" has backup; and full instrumentation and backup vocals return for the rest of C3a and all of C3b.
Outro: The outro is the melodic refrain once again.

Part IV: Conclusion (or the main points, if you want to skip the detailed sections):
There's a lot that's been fiddled with, but the main differences relate to the following points:
1. Dynamics. This is what, essentially, creates the most dramatically different changes in the songs, from the recording to the initial live version to the current one. The changes are largely created by stripping down the instrumentation in key places and reinstating it in others, and as you get further from the recorded version, the differences get more and more extreme -- to the point where the song goes directly from a cappella without a mic to a full band playing at top volume. I don't think it is possible to get more extreme than that, short of adding a 100-piece orchestra on top of the band when it comes in.
2. Switching between melodic & rhythmic playing of the guitar, most noticable in the intro & outro. Since personally, I love the melodic riff (I'm all about lilting melodies), I'm quite happy that the current version uses it in both of these places.
3. Creation of Interlude 3 in the live versions. This was probably a conscious decision that may have been planned even when the song was recorded, to get as much out of the song as possible in the live performance, but it's a good kind of change. It works well there, and probably wouldn't as much on a recording; this is also likely the reason that Interlude 1 is twice as long in the live versions as well.

So, in short: dynamics, tweaking the melody, shortening some things and lengthening others. Which is, when you think about it, largely what DC described as having done (on a more general level) in the first place ("different intros, different breaks; we'll extend stuff, shorten stuff"). And it's amazing what a profound effect these things have on a song. At this point, I'd actually venture to say that the song is as different from its original version as Permanent live is from the recording, or even more so -- and interestingly enough, for perhaps the same reasons.

Also, two other random notes I wanted to make on the song -- I'm pretty sure now, after listening to it umpteen times, that it's in 3/4 time as opposed to 6/8. It's also a very, very hard song to sing. There are large vocal jumps all over the place, the most notable in the chorus, where "So lie" is sung with a difference of an octave between the notes. And this, IMO, makes the a cappella even more impressive -- because singing that without the safety net of instrumentation is really rather gutsy. And as we've discussed recently, singing it without the mic -- however that's accomplished -- just highlights what an incredible instrument David's voice really is. He's said in the past that, in relation to his fellow AI finalists, he doesn't have the best voice. I think that this particular aspect of his Lie performance proves that he is at least comfortable enough with his voice's strong points to showcase it that way.

And finally -- this is where I get to be a little poetic. I've been trying to come up with the words to accurately describe the live performance I was lucky enough to see -- in particular the a cappella. I think I finally have. So, alphabetically:
Astounding. Audacious. Brilliant. Ethereal. Transcendent.