Pitch Articulation System For An Electronic Organ

Abstract

A pitch articulation system for an electronic organ in which the normal organ sound or voice receives an additional low frequency amplitude or frequency modulation for a short period of time upon depressing each key. Upon depressing a key, a pulse forming circuit is triggered which produces a pulse of a selected duration. This pulse keys a vibrato or a tremolo oscillator for a period of time equal to the pulse's duration.

Description

This invention relates to a pitch articulation system for an electronic organ. More particularly, the present invention relates to a pitch articulation system for an electronic organ wherein an added vibrato or tremolo modulation is applied to the voice of the organ for a short period of time after the depression of a key.

In U.S. pat. No. 3,515,792 by Ralph Deutsch entitled Digital Organ and assigned to the assignee of the present invention, there is disclosed a digital organ which may be used in combination with one embodiment of the present invention. The teachings of this patent are incorporated herein by reference.

U.S. pat. No. 3,515,792 discloses, in part, a digital organ having keys, a wave shape memory, a frequency synthesizer and a digital to analog converter. A digital representation of a selected musical wave shape is stored in the wave shape memory. In particular, the amplitude of the selected wave shape is sampled at a plurality of spaced points along the wave. The amplitude at each sample point, or the difference between the amplitude at adjacent sample points, is digitized; that is, the numerical value in discrete units of amplitude is assigned to each point. Representations of these digital amplitude or amplitude difference values are stored in the wave shape memory. The wave shape memory may be any suitable electronic memory such as a diode array.

To produce a musical note, the stored digital representation of the wave shape is repetitively read from the wave shape memory at a rate depending upon the key selected. In other words, the depressing of a particular key causes the frequency synthesizer to produce a particular frequency. This frequency produced by the frequency synthesizer may be integrally related to the first harmonic frequency of the note of the key depressed. The frequency signal produced by the frequency synthesizer is used to sequentially read out of the wave shape memory the amplitude or amplitude increment at each sample point. The digital signal sequentially read out of the wave shape memory is then converted by the digital to analog converter to an audio signal. The audio signal may then be amplified by audio amplifiers and applied to speakers.

The present invention is directed to a pitch articulation system for use in an electronic musical instrument such as an electronic organ. In an electronic organ, pitch articulation is desired in order to produce an electronic organ which is acceptable to the most discriminating organist. The present invention concerns an important element in the electronic production of realistic organ tone. This element is the presence of speech transients in a given note or tone source.

The present invention applies an added vibrato or tremolo modulation to an existing organ note or tone for a short period of time after a key is operated or depressed. Accurately described, tremolo is a variation of volume or amplitude modulation, while vibrato is a variation of pitch or frequency. However, it is not easy to tell merely from the sound whether tremolo or vibrato is being used because of the relatively small degree of change and the rate at which it occurs. Professional musicians judging only by the sound can be mistaken. Therefore, in the present application, when speaking of vibrato, it is understood that tremolo may also be used or vice versa.

The present invention advantageously produces a pleasing effect and more realistic tone or voice by adding a tremolo or vibrato for a short period of time upon operation of a key. This period of time may be, in one specific sample, seventy milliseconds. However, it is understood that this period of time may be longer or shorter.

In one embodiment of the present invention, a pulse forming circuit is energized by depressing or operating one of the keys. This pulse forming circuit generates a pulse when energized. The pulse from the pulse forming circuit may be used to energize a tremolo or vibrato oscillator, close a switch, or gate the output of the oscillator for a period of time equal to the duration of the pulse. This short duration tremolo or vibrato is applied to the normal musical instrument or organ voice.

In another embodiment of the present invention, the tremolo or vibrato oscillator output is applied to digital representations of a musical note wave shape stored in a wave shape memory as it is read out of the memory. The output of the oscillator may be applied through a circuit which may selectively invert the oscillator output. In other words, the tremolo or vibrato output can be either added to or subtracted from the normal organ output.

For the purpose of illustrating the invention, there are shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a block diagram of an apparatus for performing the present invention.

FIG. 2 is a block diagram of another embodiment in accordance with the present invention.

Referring now to the drawings in detail, there is shown in FIG. 1 an embodiment of the invention wherein a switch 10 is operated by a key (not shown) of an electronic organ. Switch 10 may be provided with an arm 12 which when operated simultaneously connects contacts 14 and 16 to point 18. Contact 16 may be connected to keying circuitry providing the normal organ voice without the addition of the pitch articulation of the present invention. Terminal 20 may be ground potential or some other suitable potential which enables operation of pulse forming circuitry 22 and the normal organ circuitry through contact 16. However, it is understood that the switch shown by FIG. 1 is not intended to be limiting. For example, the normal organ circuitry could be connected to point 18 thereby eliminating the additional contact point 16.

Pulse forming circuit 22 generates a pulse upon the closing of switch 10. The pulse generated by pulse forming circuit 22 may be used to hold a switch 24 closed for a period of time equal to the duration of the pulse. Switch 24 energizes or enables the system vibrato 26 during the time duration of the pulse formed by pulse forming circuit 22.

Referring now to FIG. 2, there is shown another embodiment of the invention. Organ keys 30, frequency synthesizer 32, wave shape memory 34 and digital to analog converter 36 may be similar to those described in U.S. pat. No. 3,515,792. The organ keys 30 in addition to energizing frequency synthesizer 32, energize pulse forming circuitry 38. Pulse forming circuitry 38 produces a pulse of a desired pulse width. The pulse width of the pulse generated by pulse forming circuitry 38 may be 70 milliseconds, however, it may be shorter or longer as desired to suit the personal taste of the listener.

The pulse formed by pulse forming circuit 38 energizes tremolo oscillator 40 (which in an alternative embodiment may a vibrato oscillator) for the duration of the pulse. The output of the tremolo oscillator 40 is fed through an adder-subtracter circuit 42. Adder-subtracter circuit 42 may be an inverter circuit in which it is possible to select either an inverted or a non-inverted output. The output of the adder-subtracter circuit 42 is fed through stop tabs 44 to wave shape memory 34. The stop tabs 44 enable a choice by the organist as to whether the added pitch articulation will be used. The output of adder-subtracter circuit 42 fed through stop tabs 44 is applied to the digital signal being sequentially read out of the wave shape memory. That is, where the amplitude of the digital pulse represents the amplitude at that point of the stored musical signal, the signal fed through stop tabs 44 is algebraically added to it. Alternatively, the signal fed through stop tabs 44 may be applied to the signal being sequentially read out of wave shape memory 34 in digital to analog converter 36 as shown by the dotted line in FIG. 2. Referring to FIG. 1 of U.S. pat. No. 3,515,792-Deutsch, the pitch articulation signal may be applied to the signal read out of wave shape memory 24 as it is read out either in wave shape memory 24, digital to analog converter 30 or any other suitable stage after the signal is read out of wave shape memory 24. A still further alternative is the applying of the output signal from stop tabs 44 to the signal addressing or reading out of wave shape memory 34. This would vary the rate at which the signal stored in the wave shape memory 34 is read out. Referring to FIG. 1 of United States pat. No. 3,515,792-Deutsch, the output of stop tabs 44 would be applied to the signal addressing wave shape memory 24. By means of the adder-subtracter circuitry, this added tremolo may be added to or subtracted from the digital signal being read out of the wave shape memory 34. Suitable circuits for the adder-subtracter circuitry are circuits SN 54181 or SN 74181 available from Texas Instruments, Inc., Dallas, Texas 75222.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

Claims

I claim:

1. A pitch articulation system for use in an electronic musical instrument having keys and a vibrato system, comprising:

switch means activated by said keys in response to said keys being depressed;

a pulse forming circuit energized by said switch means in response to said switch means being activated, said pulse forming circuit generating a pulse when energized; and

means for enabling said vibrato system of said electronic musical instrument in response to the pulse of said pulse forming circuit for the duration of the pulse generated by said pulse forming circuit.

2. A pitch articulation system as recited in claim 1 wherein said enabling means is a switch.

3. A pitch articulation system as recited in claim 1 wherein said enabling means is an electronic switch.

4. A pitch articulation system as recited in claim 1 wherein said pulse forming circuit generates a pulse having a duration of 70 milliseconds.

5. A pitch articulation system for use in an electronic musical instrument having keys and a tremolo system, comprising:

switch means activated by said keys in response to said keys being depressed;

a pulse forming circuit energized by said switch means in response to said switch means being activated, said pulse forming circuit generating a pulse when energized; and

means for enabling said tremolo system of said electronic musical instrument in response to the pulse of said pulse forming circuit for the duration of the pulse generated by said pulse forming circuit.

6. A pitch articulation system as recited in claim 1 wherein said enabling means is a switch.

7. A pitch articulation system as recited in claim 1 wherein said enabling means is an electronic switch.

8. A pitch articulation system as recited in claim 5 wherein said pulse forming circuit generates a pulse having a duration of seventy milliseconds.

9. An electronic musical instrument having keys, a wave shape memory for storing digital representations of musical sound at sampled points, a frequency synthesizer for producing a frequency signal for reading digital representations out of said wave shape memory at a rate related to the key operated to form a digital signal, a digital to analog converter for converting said digital signal to an audio signal, wherein the improvement comprises:

a pulse forming circuit energized by depressing one of said keys, said pulse forming circuit generating a pulse when energized;

a tremolo oscillator, said tremolo oscillator being energized by the pulse generated by said pulse forming circuit;

means for applying the output of said tremolo oscillator to the digital signal being read out of said wave shape memory upon operation of said one of said keys.

10. An electronic musical instrument as recited in claim 9 wherein said means includes stop tabs.

11. An electronic musical instrument as recited in claim 9 wherein said means includes an adder-subtracter circuit, said adder-subtracter circuit allowing the output of said tremolo oscillator to be added to the digital signal or subtracted from the digital signal by inverting the output of said tremolo oscillator.

12. An electronic musical instrument as recited in claim 9 wherein the pulse generated by said pulse forming circuit has a duration of 70 milliseconds.