An Analysis of “Stairway to Heaven”, Part 8: Tempo

One aspect I've ignored so far is tempo. The song gradually builds speed, before winding down again at the end.

0:00-0:54 Introduction: 64 beats in 53.8 seconds = 71.4 beats per minute

0:54-1:48 Verse 1: 64 beats in 53.7 seconds = 71.5 bpm

1:48-2:15 Verse 2: 32 beats in 26.8 seconds = 71.6 bpm

2:15-2:40 Transition A 1: 32 beats in 25.0 seconds = 76.8 bpm

2:40-3:07 Verse 3: 36 beats in 27.6 seconds = 78.3 bpm

3:07-3:31 Transition A 2: 32 beats in 23.4 seconds = 82.1 bpm

3:31-3:57 Verse 4: 36 beats in 26.5 seconds = 81.5 bpm

3:57-4:20 Transition A 3: 32 beats in 23.0 seconds = 83.5 bpm

4:20-4:45 Verse 5: 36 beats in 25.5 seconds = 84.7 bpm

4:45-5:08 Transition A 4: 32 beats in 22.0 seconds = 87.3 bpm

5:08-5:35 Verse 6: 36 beats in 25.3 seconds = 85.4 bpm
NOTE: The measure that connects Verse 6 and Transition B 1 uses a fermata to artificially extend its temporal duration, which skews the numbers. To be consistent, I'm omitting that measure from this analysis.

5:35-5:56 Transition B 1: 31.5 beats in 20.1 seconds = 94.0 bpm

5:56-6:45 Solo: 80 beats in 48.8 seconds = 98.4 bpm

6:45-7:47 Verse 7
   6:45-7:27   [vocal]: 18 measures = 72 beats in 42.3 seconds = 102.1 bpm
   7:27-7:47   [instrumental]: 28 beats in 17.5 seconds = 96.0 bpm
NOTE: I'm again omitting the final measure as it uses another fermata, which skews the numbers.

7:47-8:02 Coda: freely (not in rhythm)

Here's the same information in the form of a line graph:

With two minor exceptions that fall within the margin of error, the tempo consistently increases throughout the song until the end. And this was done very much on purpose. "When I did studio work," acknowledged Jimmy Page, "the rule was always: you don't speed up. That was the cardinal sin, to speed up. And I thought, right, we'll do something that speeds up" (Wall, page 242).

Interestingly, the climax of the song as a whole comes at 5:56 (at the onset of the solo), but the tempo's climax is at 6:45 (at the onset of verse 7), where it peaks at 102 beats per minute.


SOURCES
Wall, Mick. 2008. When Giants Walked the Earth: A Biography of Led Zeppelin. St. Martin's Griffin, New York, NY.