ACOUSTICS. — As a science it deals with all the qualities of sound in itself or in relation to certain places where sounds are heard. With regard to the liturgical use of acoustics, a distinction must be made between the study of sound as an element composing chant and the sound of instruments, such as the organ and bells.
Prior to Gregorian chant, the Hellenes and Greco-Romans considered the study of sound as part of harmonics, that is, the proper arrangement of small or large intervals, diatonic or chromatic, symphonic or diaphonic, successive or simultaneous.
In liturgical use, instruments were excluded both on account of acoustics and because of their profane associations. This exclusion, however, does not apply to all instruments, since some are used to give the pitch or to prelude the chant to be performed.