txtDefinition=The arrangement of music into regular groupings of {\uldb beats}{\v 154397}. In music before 1900 most meters were either {\uldb duple}{\v 137483} or {\uldb triple}{\v 103553} and, once established, remained constant for a period of time. Mozart\'92s two outer {\uldb movements}{\v 151907} are in duple meter, while the two inner movements are in triple meter.