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
Grace note the bar in which they are contained - and therefore, do not require other notes to be dropped from the bar to keep the time signature intact. In bagpipe music there is extensive use of grace notes. Indeed, because the chanter is not tongued but supplied by a continuous air source from the bag, grace notes are sometimes the only way to differentiate between notes. For example, inserting a grace note between two crotchets (quarter notes) played at the same pitch is the only way to indicate them as opposed to them sounding like a single minim (half note). Various