THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

18.3 Duration of Musical Notes 513Figure 18.6. Eight systems used for tone identification in music (Young, 1939).18.3 Duration of Musical NotesThe duration of a musical tone is the length of time assigned to it in the musicalcomposition. Figure 18.8 displays the symbols used to indicate duration. Whilethe pitch of a tone is given by its position on the staff, its length is assigned bythe choice of one of the symbols of Figure 18.8. However, the magnitude (i.e.,its duration) of a tone is not rigidly fixed and it may vary from composition tocomposition. But nevertheless, in a particular composition the duration of eachtone is kept in proportion to the magnitude of a whole note.In the traditional musical notation a vertical bar is drawn across the staff. Thetime interval between two vertical bars in a staff is called a measure, or the lessprecise but more commonly used bar. The time intervals of all measures withina composition are usually equal. If two whole notes constitute a measure, thenthe measure will need four half notes, or eight quarter notes, or any combinationthat adds up to two whole notes in time interval. A double bar that consists of twovertical bars across the staff denotes the end of a division, movement, or an entirecomposition.To indicate periods of silence in a composition, one or more rest symbols ofFigure 18.9 is used to indicate the duration of the silence. The duration of a wholerest is equal to that of a whole note, the duration of a half rest is equal to that of ahalf note, and so forth.The duration of a tone represented by a note or a rest of a certain denominationcan be modified by the addition of a dot to the note. The effect of the dot is to