In music, the speed at which a piece should be played. One way of indicating the tempo of a piece of music is to give a metronome marking, which states the number of beats per minute; for example, ‘crotchet = 60’ means that there should be 60 crotchet beats to the minute, that is, one per second. Modern electronic metronomes measure tempo very accurately. Performers sometimes change or even ignore metronome markings, playing at a tempo that suits their interpretation of the music. However, the knowledge of performance practice gained by academic investigation into early music has encouraged performers to pay more attention to original tempo markings. Music written before the development of precise metronomes could only give a vague idea of speed, and was often notated in a confusing manner. The system of time signatures that was developed during the Renaissance used symbols which, as well as giving the number of beats per bar, gave some indications of speed. In the 17th century, tempo…