Double whole note the "brevis" was to be considered the unit of time ("tactus"), instead of the usual "semibrevis". The old symbol , used as an alternative to the numerical proportion 2:1 in mensural notation, is carried over into modern notational practice to indicate a smaller relative value per note shape. It is normally used for music in a relatively quick tempo, where it indicates two minim (half note) beats in a bar of four crotchets (quarter notes), while is the equivalent of , with four crotchet beats . Double whole note In music, a double whole note (American), breve (international), or double
Mensural notation and short notes (minims and crotchets), or groups of three short notes. In the 13th century, all of these were notated using only the longa and breve notes. A longa was automatically understood to fill a whole ternary metric group whenever it was in the neighborhood of other notes that did the same, i.e., whenever it was followed either by another longa or by a full group of three breves. When, however, the longa was preceded or followed by a single breve, then both filled a ternary group together. Thus, the longa had to be reduced to a value of