Electronic musical instrument of numerical value processing type

Claim 1

An electronic musical instrument conprising: a key switch circuit designating notes to be played by key operation; a first circuit for generating a numerical value corresponding to a frequency related to a designated not corresponding to an operated key; a second circuit for modifying said numerical value to produce a modified signal; a third circuit for producing a musical tone having a frequency corresponding to said modified signal; a fourth circuit which generates a modification coefficient of said numerical value related to the designated note; and means for supplying said modification coefficient to said second circuit to modify said numerical value; said fourth circuit including circuit means responsive to the key operation for generating a periodic signal as said modification coefficient, said circuit means having a circuit for generating said periodic signal including a portion in which the amplitude of said periodic signal increases at a predetermined rate and a succeeding portion in which the amplitude is constant, and means for varying said rate; said rate varying means including means for providing a low rate as said predetermined rate so that the increase of said amplitude of the periodic signal takes place gradually enough to be perceived by human ears, means for providing a high rate as said predetermined rate so that said increase takes place too quickly to be perceived by human ears, and means for switching said rates.