used this system in many of their works. Émile Jaques-Dalcroze proposed this in his 1920 collection, Le Rythme, la musique et l'éducation. Another possibility is to extend the barline where a time change is to take place above the top instrument's line in a score and to write the time signature there, and there only, saving the ink and effort that would have been spent writing it in each instrument's staff. Henryk Górecki's Beatus Vir is an example of this. Alternatively, music in a large score sometimes has time signatures written as very long, thin numbers covering the whole height of the score rather than replicating it on each staff; this is an aid to the conductor, who can see signature changes more easily. Early music usage Mensural time signatures In the mensural notation of the 14th, 15th and 16th centuries there are no bar lines, and the four basic mensuration signs indicate the normal ratio of duration between different note values. Unlike modern notation, the subdivisions could be either 2:1 or 3:1. The relation between the breve and the semibreve was called tempus, and could be perfect (triple 3:1 indicated by circle) or imperfect (duple 2:1, with broken circle), while the relation between the semibreve and the minim was called prolatio and could be major (3:1 or compound, indicated by dot) or minor (2:1 or simple meter). Modern transcriptions often reduce note values 4:1, such that corresponds to meter; corresponds to meter; corresponds to meter; corresponds to meter. N.B.: In mensural notation actual note values depend not only on the prevailing mensuration, but on rules for imperfection and alteration, with ambiguous cases using a dot of separation, similar in appearance but not always in effect to the modern dot of augmentation. Proportions Besides showing the organization of beats with musical meter, the mensuration signs discussed above have a second function, which is showing tempo relationships between one section to another, which modern notation can only specify with tuplets or metric modulations. This is a fraught subject, because the usage has varied with both time and place: Charles Hamm was even able to establish a rough chronology of works based on three distinct usages of mensural signs over the career of Guillaume Dufay (1397(?) – 1474). By the end of the sixteenth century Thomas Morley was able to satirize the confusion in an imagined dialogue: it was a world to