Toshio Takeda

Musical tone waveshape generator

The invention is directed to a waveshape generator capable of producing a desired waveshape by previously storing basic amplitudes obtained by sampling one period of the waveshape at a coarse interval and calculating amplitudes with a fine interval between the basic amplitudes. While basic amplitudes A and B are sequentially produced at a coarse interval in response to an integer portion of the input data, a function X (c) is produced in response to a fraction portion of the input data. Waveshape amplitudes are interpolated between the basic amplitudes by carrying out calculation of A + (B - A) × X(c) in response to these values A, B and X(c). A special form of function X(c) is also used for applying interpolation by a partial waveshape of a trigonometric function wave. An example of a musical tone waveshape generator is also described in which different waveshapes are produced depending upon different tone ranges by moving the position of a radix point for each of the different tone ranges.

Electronic musical instrument with glide

In a digital type electronic musical instrument, a glide effect is produced by digitally frequency-modulating the frequency of a musical tone in such a manner that the frequency changes quickly and smoothly. Glide information used for effecting this frequency-modulation is produced on the basis of a glide code obtained by counting a clock pulse. The glide information which changes its contents uniformly is multiplied with the basic frequency information to effect the frequency-modulation. The glide effect can be controlled for each individual keyboard. According to an embodiment of the invention, the frequency-modulation is applied to an attack portion of a musical tone only and sustain and decay portions of the musical tone are reproduced with a normal frequency so that the musical tone will be provided with a crisp, vivid musical effect.