"Dozens of critics have explained why metronome marks are more problematic than early-music enthusiasts used to acknowledge. Composers, to begin with, often take their own music faster or slower than the speeds they imagined when setting numbers to the page. Changes of mood can lead anyone (including a composer) to different tempos at different times. Besides, what sounds right inside the composer's head often needs adjustment to work with real instruments in real places. ... Insisting that there is something essential about following a metronome mark imposes a meaningless limit on performance."