(1) Data for calculating the size of the source of sound in musical instruments.
The basic parameters of the mensura in stringed instruments are the diameter, length, and tension of the strings; in wind instruments, the bore, diameter, and length of the air channel; in reed instruments, the thickness, width, and length of the reed. In stringed instruments that are played by plucking and bowing, normally the length of the working part of the string (between the axes of the nut and the bridge) is called the mensura, while in stringed percussion and keyboard-percussion instruments, the mensura is also the line along which the small hammers strike the string. In wind instruments, the mensura is the ratio of the mean diameter of the channel to its length (hence, the wide and narrow mensura). The mensura also includes the calculations for the arrangement of strings according to the width of the body of a piano (upright or grand) or width of the fingerboard; the placement of side holes in wind instruments; and the spacing of frets on stringed instruments.
(2) General name for the different types of rhythmic divisions in mensural notation.