I've already written about the first verse of 'Stairway to Heaven' in my series on rhythmic displacement, so I'll consider it only briefly here.
The first verse is structurally identical to the instrumental introduction. Both employ four phrases, each four measures long, the first two of which are identical, the last two of which are comparable and so labeled (b) and (b'). Most interesting is that Plant's second verse ("There's a sign...") begins early, at 1:34, overlapping with the fourth and final phrase of the first verse.
0:54-1:48 (A) Verse 1 (16 measures)
0:54 (a) |a E/g# |C/g D/f# | FM7 |a | “There's a lady...”
1:07 (a) |a E/g# |C/g D/f# | FM7 |a | “When she gets...”
1:21 (b) |C D |FM7 a |C G |D | “Ooo...”
1:34 (a & b') |C D |FM7 a |C D |FM7 | “There's a sign...”
Part of me wants to label the third and fourth phrases as their own distinct section. I could see this as a bridge instead of part of the verse. But bridges are defined by contrast to the verses, and while there certainly is some contrast, there is also a lot of similarity.
The first four chords of the phrase in question (C-D-FM7-a) are the same as the last four chords of the previous phrases. The harmonic rhythm is faster (covering two measures instead of three), and the chords are all in root position (no inversions this time), but there is a clear and strong harmonic similarity.
Now, there are many songs where the verses and bridges share strong harmonic similarities but there are other differences, such as melody, that distinguish the two sections. But in 'Stairway', there is also a clear and strong melodic similarity. While the first half of the phrase in question is different (“Ooo...”, shown below with blue notes), the second half employs the same pattern as the previous phrases. They even use the same lyrics (“and she's buying a stairway to heaven”, shown in red).
Finally, the lyrics suggest that these (b) phrases are not a bridge because they include the title (which was also heard earlier in the first phrase of verse 1). While it's not unheard of for the title to be lifted from the bridge (check out 'She's A Woman', 'Rain', or 'For No One' by The Beatles), it is rather rare. It's much more common for the title to be lifted from verse lyrics than from bridge lyrics.
So all of this compels me not to label it as a bridge, but as part of the verse. The contrast that is there isn't strong enough to justify an independent formal level label
Verse 2 is half as long as verse 1, and it's identical to the first half of verse 1 (save for the lyrics).
1:48-2:15 (A') Verse 2 (8 measures)
1:48 (a) |a E/g# |C/g D/f# | FM7 |a | “In the tree...”
2:01 (a) |a E/g# |C/g D/f# | FM7 |a | [instrumental]
The reason for this abbreviation is because we've heard the (a)(a)(b)(b') pattern twice already (once from 0:00-0:54 as the intro, then again from 0:54-1:48 as the first verse). To avoid any threat of monotony, this third iteration (and every subsequent iteration) is curtailed to two phrases. This truncated second verse leads to the first transition, which I'll consider tomorrow.
Aaron Krerowicz, pop music scholar
An informal but highly analytic study of the music of Led Zeppelin.