jamie found a blog entry by Paul Lamere, working for audio company Echo Nest, in which he experiments with detecting which songs use a click track. Lamere gives this background: "Sometime in the last 10 or 20 years, rock drumming has changed. Many drummers will now don headphones in the studio (and sometimes even for live performances) and synchronize their playing to an electronic metronome — the click track. ...some say that songs recorded against a click track sound sterile, that the missing tempo deviations added life to a song." Lamere's experiments can't be called "scientific," but he does manage to tease out some interesting conclusions about songs and artists past and present using Echo Nest's developer API.