Abstract: A tone source apparatus for an electronic musical instrument is characterized in that at least one cycle of a musical-tone waveform, which it is desired be produced, is depicted as a sequence of section lines and a series of pulses having regular intervals is varied, by a pulse-density varying circuit, in pulse density in accordance with the degrees of inclination of the respective section lines. The resultant series of pulses having varied pulse density is formed, by a waveform forming circuit, into the desired musical tone waveform. The pulse-density varying circuit comprises a first counter to which is applied as an input, the aforementioned series of pulses having regular intervals. A second counter is connected, in series or in parallel, to the first counter and a decoder is connected to an output terminal of the second counter. A memory circuit is connected to the output terminals of the decoder.

Abstract: A tone source apparatus is provided for an electronic musical instrument. It comprises a memory circuit which has a plurality of addresses and is so arranged that where at least one cycle of a musical tone waveform is divided into p units and a waveform in each section range is represented by a formula containing the abscissa as its variable, a coefficient and a section range quantum number of each formula is memorized in the form of digital signals in the corresponding address. Also included are a clock pulse oscillator, a counter means for counting output clock pulses of the clock pulse oscillator, and a coincidence circuit serving to generate the coincidence signal when the output digital signal of the counter means and a digital signal of the section range quantum number memorized in the memory circuit coincide with one another. A decoder designates the next stage address in order by output signals of the coincidence circuit.

Abstract: An apparatus for forming a musical-tone waveform for an electronic musical instrument characterized in that at least one cycle of a musical-tone waveform, which it is desired be produced, is divided in amplitude by dividing lines at equal intervals and sampling points on a time axis are determined from respective crossing points between the waveform and the dividing lines and the distance between the initial and the final sampling points is represented by an appropriate number of pulses so that each sampling point may be represented by a pulse number. There is further provided a memory circuit wherein each sampling point, that is, the pulse number thereof is set up in the form of a digital signal. Additionally, there is a set up in the form of a digital signal a tendency such as increase, decrease or equal at each sampling point with reference to the preceding sampling point.