LONDON, ENGLAND - AUGUST 14:   The pendulum of a metronome moves during the rehearsal for composer Gyorgy Ligeti's 'Poeme For 100 Ticking Metronomes' for Prom 44 of the BBC Proms at Royal Albert Hall on August 14, 2012 in London, United Kingdom.  (Photo by Amy T. Zielinski/Redferns via Getty Images)