Whole note rest may also be used in music of free rhythm, such as Anglican chant, to denote a whole measure. A whole note (American) or semibreve (British) is a musical note represented by a hollow oval note head—like a half note (or "minim")—and no note stem (see Figure 1). Its length is equal to four beats in time, that is the whole measure (or bar). Most other notes are fractions of the whole note. Half notes last for one half the duration of the whole note, quarter notes (or "crotchets") last for one quarter the duration, and a double whole note
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