Abstract: The system comprises a frequency number memory device for storing information regarding the frequencies of respective tones, a keyboard switch for reading out frequency number information corresponding thereto from the memory device, an address generator including an adder for adding a predetermined number of the frequency number information thereby producing an address signal consisting of plural bits, address composers for processing the bits of the address signal and thereby composing digital tone signals constituting a saw-tooth, square and triangular waveshape, and digital-analog converters for converting the digital tone signals into analog tone signals, which are thereafter used to synthesize waveshapes of any tone.

Abstract: An electronic musical instrument capable of changing a slope portion of a filter characteristic continuously from start to completion of production of a musical tone.The inventive electronic musical instrument changes a filter slope in a frequency region above or below a cut-off frequency with lapse of time and, in order to achieve such change in the filter slope, changes a slope factor continuously from start to completion of production of the tone. The instrument is also capable of changing the cut-off frequency.An example of a low-pass filter is shown in which a desired form of a successively changing filter slope can be obtained by employing four slope factor values and three values representing a speed of change of the slope factors as well as three cut-off frequency values and two values representing a speed of change of the cut-off frequencies.

Abstract: An electronic musical instrument wherein instantaneous amplitude values of respective harmonics of a musical tone waveform are individually provided in accordance with a numerical value corresponding to the frequency of the depressed key for the musical tone, each of harmonic amplitude coefficients setting relative amplitudes of the respective harmonics is multiplied with corresponding one of the instantaneous amplitude values and the multiplication products are aligned with respect to time thereby to obtain a musical tone of a desired tone color, i.e. of a desired frequency spectrum construction. The harmonic amplitude coefficients are given as values corresponding to a multipeak spectrum construction.The harmonic amplitude coefficients are provided by a filter having a multipeak characteristic.

Abstract: The electronic musical instrument according to the invention produces excellent tone color effect by changing filter characteristics discontinuously from the start of generation of a musical tone.A plurality of filter characteristics each represented by a deflecting line consisting of straight lines (these filter characteristics being different from each other in coordinates at each point of deflection as well as inclination of each straight line) are stored in memory. These filter characteristics are sequentially read out with the lapse of time and level information of each harmonic constituting a musical tone is obtained by calculating a primary functional formula of the straight line region in which the read out filter characteristic belongs. The level of each harmonic is controlled in response to this level information.

Abstract: An electronic muscial instrument capable of calculating level information of slope portion of a filter characteristic on the basis of the inclination of the slope and the cut-off frequency without requirement of storing level information of the slope portion for each individual frequency.The inventive electronic musical instrument is also capable of obtaining level information of an acute portion of filter characteristic which constitutes selectivity Q by calculating the inclination and peak value of the acute portion and difference between the peak frequency and the cut-off frequency.An example is shown in which the cut-off frequency is caused to successively change during a period of time from the start to the end of playing of a musical tone and in which the peak of the selectivity Q can be directed either upward or downward as desired.

Abstract: An electronic musical instrument capable of producing a multi-system tone source effect which is an effect providing a musical tone with naturalness and resulting from simultaneous playing of a tone of a proper pitch and a tone of a pitch slightly different from the proper pitch. The inventive electronic musical instrument produces this effect with a smaller number of tone source devices than the number of systems.Composite musical tone waveshape amplitudes achieving the multi-system tone source effect can be represented by a single multiplication term of a sine waveshape function content corresponding to a certain pitch and a cosine waveshape function content corresponding to a pitch difference. According to the invention, the sine waveshape function content and the cosine waveshape function content are separately produced and these contents are multiplied with each other to produce the composite musical tone waveshape amplitudes.

Abstract: An electronic musical instrument capable of producing a large number of harmonic contents with a small number of calculation circuits. A composite wave consisting of plural harmonics can be mathematically expressed as a multiplication of a factor including an order number of a harmonic and a factor or factors not including an order number of a harmonic. The instrument according to the invention utilizes this principle and produces a composite wave by first obtaining these two kinds of factors individually and thereafter multiplying them together.An example of the invention capable of calculating four harmonics simultaneously and another example capable of calculating two harmonics simultaneously are described.

Abstract: An electronic musical instrument capable of producing any desired combination of two tones of mutually different footage. According to the invention, such combination of tones can be produced from only two tone sources without providing tone sources of an equal number to a total number of footage to be coupled. In view of the fact that musical tone waveshape amplitudes of two coupled tones of different footage can be represented by a multiplication term of a sine wave content and a cosine wave content, these two waveshape contents are individually calculated and then combined to form amplitudes of a composite musical tone waveshape.