This is great. A programmer came up with a way to plot graphs of the beat durations of songs in order to determine which songs used a click track. His synopsis of the Beatles‘ “Dizzy Miss Lizzy”:
This plot shows the beat duration variation (in seconds) from the average beat duration over the course of about two minutes of the song (I trimmed off the first 10 seconds, since many songs take a few seconds to get going). In this plot you can clearly see the beat duration vary over time. The 3 dips at about 90, 110 and 130 correspond to the end of a 12 bar verse, where Ringo would slightly speed up.
He compared this to songs by Britney Spears, Weezer, Green Day, Metallica, Nickleback, and others. Fascinating stuff. Let’s hope he posts more!