Method and apparatus for tuning an electronic keyboard instrument in pure scale are disclosed herein. The apparatus comprises frequency modifier means such as potentiometers which are electrically associable with the normal tone generators of the instrument, said frequency modifier means being adjustable so as to influence a tone produced by said generator to have a particular frequency or pitch, and switching means for grouping said frequency modifier means for playing in a particular key. The switch means may be mechanical or electronic and a plurality of frequency modifier means are provided for each tone generator, preferably 12. The method of tuning the instrument in pure scale comprises providing the instrument with the tone generators in tune, electrically associating the frequency modifiers with the tone generators and thereafter tuning each generator in selected keys. The instrument will then play in pure scale in any particular key that is selected by the switch means. Additionally, a further set of frequency modifier means may be provided for selectively enabling the instrument to play in tempered scale.
In a digital type electronic musical instrument in which frequency information corresponding to a depressed key is cumulatively counted and a musical tone waveshape is read from a memory by the resultant output of the cumulative counting, modified frequency information is produced by adding to or subtracting from said frequency information second frequency information represented by a predetermined frequency difference. A tone of a pitch which is slightly different from a normal pitch is generated from this modified frequency information for producing a beat effect between notes in an octave relation. The pitch can be controlled by suitably adjusting the second frequency information. Different beat effects can be produced for respective keyboards by varying the second frequency information by each keyboard. According to an alternative embodiment of the invention, two or more sets of tone reproduction systems are provided and the beat effect is produced by depression of a single key by varying modified frequency information for the respective tone reproduction systems.
In a digital type electronic musical instrument in which basic frequency is cumulatively counted and a musical tone waveshape is read from a memory by the resultant output of the cumulative counting, a desired vibrato effect is produced by digitally frequency-modulating the basic frequency. Vibrato information for effecting the frequency-modulation is produced from a vibrato code obtained by counting a clock pulse and a vibrato depth signal and has contents which change as time elapses. The frequency-modulation is made by multiplying the basic frequency with the vibrato information. The vibrato depth may be controlled for each individual keyboard. Vibrato frequency may be changed by changing the frequency of the clock pulse for each keyboard. According to an embodiment of the invention, the vibrato depth progressively increases from the start of reproduction of the musical tone. The speed of change of the vibrato depth may also be controlled for each individual keyboard.
A frequency divider for a tone source for an Arabian scale in an electronic organ of the type wherein musical tone signals for a standard musical scale, musical tone signals higher than the same by 50 cents and musical tone signals lower than the same by 50 cents can be obtained from the output signal of a main oscillator. The output signal of the main oscillator is frequency-divided by at least one frequency divider to obtain an output signal. The aforesaid frequency divider comprises a counter and an AND circuit. An input terminal of the frequency divider is connected through the counter to an input terminal on one side of the AND circuit and is connected directly to an input terminal on the other side of the AND circuit.
Apparatus for adjusting the tuning of a musical instrument to cause the instrument to sound in just intonation while the instrument is being played comprises a data base in memory for storing an array of just intonation tone identifiers. The tone identifiers in the array are arranged by key, chordal root and tone according to just intonation relationships defined by the ratios of a scale selected by the musician. A selector unit is provided for enabling a musician to select a key and/or a chordal root, as a result of which a CPU retrieves from the array a set of tone identifiers in just intonation corresponding to the selected key or chordal root and transmits them to the sounding means of the instrument.
A pitch changing apparatus shifts the absolute pitch of musical output from an electronic organ. The apparatus combines two or more transposing switches in a cascade arrangement. In the preferred embodiment, the apparatus comprises four binary transposing switches in cascade relationship, with frequency divider circuits interposed between successive transposing switches. The preferred embodiment selects one out of twelve absolute pitches for the musical output in steps of one semitone. Other embodiments select absolute pitch in steps of two or three semitones. The other embodiments use arrays of electronic switching elements included in integrated circuit packages.
