Electronic stringed instrument - Patent Review 4817484

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic stringed instrument, and, in particular, an electronic stringed instrument which can select a specific musical parameter, such as a timbre or a rhythm pattern by picking operation of strings.

2. Description of the Related Art

A known example of an electronic stringed instrument is a guitar synthesizer which is shaped like a guitar and has a synthesizer installed therein.

Guitar synthesizers can be classified into two types: the pickup type and the trigger type, on the basis of the system used for detecting a musical input entered by a player.

The pickup type synthesizer generally uses pickup sensors (typically, magnet type acoustic sensors) for independently detecting the vibrations of the individual strings. Since the output of each pickup sensor includes multifarious overtone or harmonic components in addition to a fundamental frequency component, this fundamental frequency component is therefore extracted from the sensor output by pitch extraction means. In addition, the timing at which string vibration starts and ends is detected by analyzing the level of the output of each pickup sensor.

When fundamental frequency data is extracted from the string vibration data and a condition to indicate the beginning of string vibration is met, a processor sends pitch data corresponding to the extracted fundamental frequency data to an internal or external sound source, so as to instruct generation of a musical tone of the associated string.

Then, when a condition for indicating the end of string vibration is satisfied, the processor instructs the sound source generating the musical tone to cease tone generation.

In contrast, the trigger type guitar synthesizer generally has a string trigger switch or a string trigger detector provided one for each string, for detecting the beginning of the string vibration, and has fret switches arranged in a fingerboard, for detecting the position operated on the fret with respect to each string. The fret switches can be an ON/OFF type arranged in a matrix on the fingerboard, a tablet coordination detection type, or a type in which conductive strings to be supplied with a minute current are stretched on the fingerboard and fret contacts are provided where each string is depressed.

When the beginning of a string vibration is detected through the string trigger switches or string trigger detectors, the processor reads out fret-operated position data (data attained through the fret switches) of a triggered string, prepares pitch data from the fret position data and the data of the string that has just started vibrating, and instructs an internal or external sound source to generate an associated tone. As a result, the sound source generates a tone having a specified pitch.

With either type of guitar synthesizer, a string-picking input entered by a player is utilized for no other purpose than to control the tone generated of the sound source and to control a short-duration parameter such as the pitch of the tone to be generated. However it is considered desirable that the player of the synthesizer be able to select other tone parameters (e.g., timbre) in addition to pitch. For instance, a guitar synthesizer having a communication function such as MIDI (Musical Instrument Digital Interface, which is the international standard for coupling musical instruments or mutual communication therebetween) generally has its communication line coupled to an external musical instrument or sound source module having a similar communicating function. With the use of such a guitar synthesizer, a timbre selection is likely to be executed while the synthesizer is being played. In such a case, the player or user should operate the timbre select switch provided on a panel of the external sound source module or the like to select the desired timbre of a tone to be generated. This necessitates that the user move to where a separated sound source module is located, every time the timbre change is needed. This is very troublesome to users. This may be solved by providing a timbre select switch on the main body of the guitar synthesizer; however, to ensure selection of a number of timbres (e.g., above 50 timbres), the same number of timbre select switches are required. Provision of many timbre select switches in the narrow guitar body not only increases the manufacturing cost of the synthesizer but also is difficult in consideration of the narrow space available in the guitar body.

The same problem would be raised in selecting other tone parameters, such as various rhythm patterns and various rhythms.

Recently, there has been proposed an electronic stringed instrument in which, with a specific function switch being depressed, for example, depressing the first fret of the first string changes the musical tone to a piano tone and depressing the second fret of the first string changes the musical tone to a string tone (as disclosed in the Japanese Patent Disclosure No. 62-47698). For instrument players, however, it is more natural and desirable to directly perform the picking of a string in order to select a musical tone with a specific timbre than to depress a specific fret position for the same purpose. If a timbre selection is performed by depressing a specific fret position, it is not easy for a player to sense what kind of timbre is actually selected.

SUMMARY OF THE INVENTION

The present invention has been developed to overcome the above conventional problems, and it is therefore an object of this invention to provide an electronic stringed instrument, which expands the limited function of conventional picking signal input devices so that the output of the same picking signal input device can also be used for other purposes, particularly, for selection of other tone parameters, and which prevents deterioration of the operability due to the functional expansion.

It is another object of this invention to provide an electronic stringed instrument which eliminates the need for providing a number of musical tone parameter select switches on a narrow instrument main body to select a desired musical tone parameter and needs a simple picking signal input operation to quickly and easily select the desired musical tone parameter.

It is a still another object of this invention to provide an electronic stringed instrument in which, in selecting a musical tone parameter, when a plurality of strings are erroneously triggered simultaneously by the picking operation or when the picking of strings is performed with an open-string operational status, it is possible to assuredly prevent an unintended musical tone parameter from being set.

Development and Operation of the Invention

The mode selecting section used in this invention can be designed so as to be able to select a desired mode not only from two modes but also from among three or more modes. This feature can be realized by the use of a mechanical rotary switch or a rotary switch (structurally, a two-position switch) which electronically advances the mode.

According to one arrangement, a timbre select mode can be set by the mode selecting section. In the timbre select mode, a picking signal, such as a pitch designation signal or a string vibration period signal, is given from the picking signal input device. Musical tone parameter setting means selects one of plural pieces of timbre data based on the received picking signal. This timbre data determines the timbre of a musical tone to be generated by an internal or external sound source. In a normal play mode, therefore, the musical tone with the selected timbre is generated.

In another arrangement, a rhythm select mode can be set by the mode selecting section. In this rhythm select mode, the picking signal is given from the picking signal input device. The musical tone parameter setting means selects one of plural pieces of rhythm pattern data based on the received picking signal. In an automatic rhythm play mode, therefore, a rhythm sound is automatically produced in accordance with the selected rhythm pattern data.

In a pickup type picking signal input device, the fundamental frequency data (as well as string number data indicating which string has been picked) of a vibrating string is given by pitch extraction means for each string, which is included in the picking signal input device. The musical tone parameter setting means determines or presumes the fret operation position of that string from the given fundamental frequency data. Then, the parameter setting means converts data of the fret operation position and the string number data into a musical tone parameter, for example, using a conversion table or through some computation.

In a trigger type picking signal input device, the fret operation input through a fret switch indicates which fret of which string has been operated. Further, the string trigger input from a string trigger switch o a string trigger detector indicates which string has started vibrating and when. Therefore, based on the fret operation position data and the string number data, the musical tone parameter setting means prepares an associated musical tone parameter at the timing of the string trigger input.

One preferable conversion logic is that, with the string number being expressed by a row number 1 and the fret operation position (fret number) being expressed by a column number c, a single (1, c) is converted into the value or number n of one musical parameter. In this case, provided that all the areas on the fiberboard are effective, different or various types of musical parameters whose quantity corresponds to the value of the fret quantity x the string quantity are available for selection. For instance, with regard to timbres, a specific timbre corresponding to the combination of a specific fret number and a specific string can be selected from a group of timbres equal in number to the fret quantity x the string quantity. Such one-to-one correspondence will not deteriorate the operability of the instrument.

Another conversion logic may also be used. For instance, it is possible to determine the value or number of a single musical parameter from a combination of two fret numbers F1 and F2 and two string numbers N1 and N2 (F1, N1 : F2, N2). In this case, the total number of selectable musical tone parameters is far greater than the one attained in the former case (about M.sup.C 2; M being the string quantity+ the fret quantity).

When new data is set as a musical tone parameter, a tone generation instructing section informs a user of the content of the set musical tone parameter by means of a sound only if the content indicates that the tone should be generated. For instance, when a new timbre is set, a musical tone with that new timbre is generated so as to inform the user of the content of the set musical tone parameter. When a new rhythm pattern is set, a sound source is driven with that rhythm patter to produce the associated rhythm sound to the outside, thus informing the user of the content of the set rhythm pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary perspective view of an electronic stringed instrument according to a first embodiment of this invention;

FIG. 2 is a diagram illustrating the overall structure of the first embodiment in use;

FIG. 3 is a circuit diagram of a peak detector shown in FIG. 2; FIGS. 4A to 4E are timing charts of signals at individual components of the peak detector;

FIG. 5A is a flowchart illustrating an interrupt process executed by a microcomputer for pitch extraction at the time a zero cross from a positive peak is detected;

FIG. 5B is a flowchart illustrating an interrupt process executed by the microcomputer for pitch extraction at the time a zero cross from a negative peak is detected;

FIG. 6 is a flowchart for a mode-originated process executed by the microcomputer;

FIG. 7 is a detailed flowchart of a normal play process shown in FIG. 6;

FIG. 8 is a detailed flowchart of a timbre setting process shown in FIG. 6;

FIG. 9 is a diagram illustrating a logic for determining a timbre from a string number and a fret number;

FIG. 10 is a perspective view of an electronic stringed instrument according to a second embodiment;

FIG. 11 is a cross-sectional view taken along the line XI--XI in FIG. 10, illustrating a fret switch;

FIG. 12 is a cross-sectional view taken along the line XII--XII in FIG. 10, illustrating a string trigger switch;

FIG. 13 is a diagram illustrating the overall structure of the second embodiment in use;

FIG. 14 is a timing chart for explaining the operation of peripheral units of a latch circuit shown in FIG. 13;

FIG. 15 is a general flowchart for a microcomputer shown in FIG. 13;

FIG. 16 is a flowchart illustrating a normal play process included in mode-originated processes executed by the microcomputer in a string trigger detecting process shown in FIG. 15;

FIG. 17 is a flowchart illustrating a timbre setting process included in the mode-originated processes executed by the microcomputer;

FIG. 18 is a diagram illustrating the overall structure of an electronic stringed instrument according to a third embodiment;

FIG. 19 is a general flowchart for a microcomputer shown in FIG. 18;

FIG. 20 is a flowchart illustrating a more-originated process executed by the microcomputer in the string trigger detecting process shown in FIG. 15;

FIG. 21 is a detailed flowchart of a rhythm select process shown in FIG. 20;

FIG. 22 is a flowchart illustrating a timbre setting process involved in a fourth embodiment;

FIG. 23 is a detailed flowchart illustrating a rhythm select process involved in a fifth embodiment;

FIG. 24 is a flowchart illustrating a timbre setting process involved in a sixth embodiment;

FIG. 25 is a flowchart illustrating a rhythm select process involved in a seventh embodiment; and

FIG. 26 is a general plan view of another type of an electronic instrument to which this invention is applicable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be explained below in detail referring to the accompanying drawings.

[First Embodiment (FIGS. 1-9)]

Instrument Main Body (FIG. 1)

The main body of an electronic stringed instrument according to the first embodiment is illustrated in FIG. 1. As illustrated, the stringed instrument main body comprises a body 1, a neck 2 and a head 3 and has an outline of a guitar. A plurality of strings 4 (six strings in this example) are stretched along the length of the main body. Specifically, each of strings 4, stretched on a fingerboard 8, has one end adjustably supported by a peg 7 and the other end secured to a bridge 13 provided on body 1. String-vibration pickup sensors MN for individually pick up the vibrations of the respective strings are provided in front of bridge 13. These pickup sensors M may be constituted by a piezoelectric or magnet type microphone. Sensor signals from pickup sensors M are sent to a peak detector (sensor interface) 40 (which will be described later) where extract of a timing signal at a peak and A/D conversion of the sensor signals are performed. When picking of a string on fingerboard 8 is performed with the string depressed at an arbitrary fret 12 by a finger or the like, the associated sensor M generates a sensor signal. Fundamental frequency data of the signal represents a frequency concerned with the string length between bridge 13 and the position of the depressed fret, the material and the tension of the string, etc. The sensor signal includes various harmonic components mixed in the reference frequency data.

A mode switch MSW is provided on body 1 according to this invention. According to this embodiment, mode switch MSW is designed to selectively set a normal play mode and a timbre select mode (which will be described later in detail). For diagrammatic simplicity, other panel switches are not illustrated.

The electronic stringed instrument as shown in FIG. 1 is a MIDI instrument which can be coupled to an external MIDI instrument, etc. In the illustrated example, the instrument is coupled to an external sound source 70 through a cable C for carrying a serial asynchronous MIDI signal, and a musical tone signal generated by this sound source 70 is put through a sound system 100 for tone generation.

Overall Circuit Structure (FIG. 2)

FIG. 2 illustrates the overall circuit structure of the electronic stringed instrument according to the first embodiment. On the left side of the two-dot chain line is the main body of the electronic stringed instrument and on the right side of the line is an external section of the main body. The general control of the electronic stringed instrument is executed by a microcomputer 30. A switch status detector 50 detects the status of each of panel switches PSW on the instrument main body including the aforementioned mode switch MSW, and is constituted by a known circuit. A MIDI interface 60 is a known circuit constituted by a UART (Universal Asynchronous Receiver & Transmitter). MIDI interface 60 has a transmission section for transmitting data from microcomputer 30 to an external unit in the format which meets the MIDI standard. The transmitted signal is received by a reception section of a MIDI interface 80 of external sound source 70. Tone control data associated with the received signal is sent through MIDI interface 80 to a tone generator 90, which in turn executes preparation of a musical tone, etc.

Peak detector 40 which processes the sensor signals from pickup sensors M will now be explained in detail.

Peak Detector (FIG. 3)

FIG. 3 illustrates a peak detector (denoted by 40-1) for one channel. M1 is a pickup sensor output terminal of, for example, the first string. INT.sub.a1, CL.sub.a1, INT.sub.b1, CL.sub.b1 and L.sub.1 are signals transmitted between peak detector 40-1 and microcomputer 30. INT.sub.a1 is a signal which indicates the point where the pickup sensor signal representing the string vibration reaches the positive peak (MAX) and is given to microcomputer 30 as an interrupt signal. CL.sub.a1 is a reset signal given to peak detector 40-1 from microcomputer 30. INT.sub.b1 is a signal which indicates the point where the string vibration signal from pickup sensor output terminal M1 reaches the negative peak (MIN) and is given to microcomputer 30 as an interrupt signal. CL.sub.b1 is a reset signal given to peak detector 40-1 from microcomputer 30. L.sub.1 is a latch signal which indicates that the positive or negative peak value of the string vibration signal from pickup sensor output terminal M1 has been subjected to A/D conversion and held, and is sent to microcomputer 30 from peak detector 40-1.

The internal structure of pickup sensor 40-1 is as illustrated in FIG. 3; the sensor signal from pickup sensor output terminal M1 is amplified in an amplifier 2 and is supplied to a low-pass filter 3 where a undesirable harmonic component of the signal is removed (the cut-off frequency fcl being about four times the frequency of an open string). FIG. 4A exemplifies the output a of low-pass filter 3. As should be obvious from the figure, the waveform of the string vibration signal from pickup sensor output terminal M1 has an overtone component added to the reference frequency data. The filtered signal a is supplied to a positive peak detector 4 (MAX), a negative peak detector 5 (MIN), a zero cross detector 6 (Zero) and an A/D converter 11.

Positive peak detector 4 detects the point of the positive peak of the string vibration signal while negative peak detector 5 detects the point of the negative peak of that signal. FIG. 4B exemplifies the output signal of positive peak detector 4.

Zero cross detector 6 detects the zero cross of the string vibration signal and inverts its output. For instance, this detector 6 has a high level output while the string vibration signal is in a positive duration and has a low level output while it is in a negative duration. FIG. 4C exemplifies the output of zero cross detector 6.

A pulse signal b from positive peak detector 4 sets a flip-flop 14 and a pulse signal from negative peak detector 5 sets a flip-flop 5. FIG. 4D exemplifies the output of flip-flop 14. At the time the output of zero cross detector 6 becomes a low level (i.e., at the time the string vibration signal zero-crosses from the positive to the negative), an AND gate 24, which receives the output of flip-flop 14 and an inverted output of zero cross detector 6 through an inverter 30A, sends the set output of flip-flop 14, which indicates the occurrence of the positive peak, to microcomputer 30 as interrupt signal INT.sub.a1. Therefore, interrupt signal INT.sub.a1 being active means that the zero cross of the string vibration signal from the positive level to the negative level has occurred after this signal reached the positive peak. FIG. 4E illustrates an example of interrupt signal INT.sub.a1. Similarly, an AND gate 25 renders its output or an interrupt signal active and sends it to microcomputer 30 when the zero cross of the string vibration signal from the negative level to the positive level occurs after this signal has reached its negative peak (after flip-flop 15 is set).

Upon reception of interrupt signal INT.sub.a1 or INT.sub.b1, microcomputer 30 resets the associated flip-flop 14 or 15 using signal CL.sub.a1 or CL.sub.a2. In response to signal L.sub.1, microcomputer 30 reads the content of a latch 12 or the digital value of the positive or negative peak value of the string vibration signal.

The input and output signals of pickup sensor 40-1 will further be discussed below. The duration of output signal INT.sub.a1 being active corresponds to the time from the point when the string vibration signal is at its positive peak to the point when this signal is at the next positive peak. More specifically, signal INT.sub.a1 becomes active at the time the string vibration signal, after reaching its positive peak, zero-crosses to the negative level and becomes active again at the time the string vibration signal, after reaching the positive peak again, zero-crosses to the negative level (see FIG. 4A). The duration of output signal INT.sub.b1 being active ranges from the point when the string vibration signal, after reaching the negative peak, zero-crosses to the positive level to the point when the string vibration signal, after reaching the negative peak again, zero-crosses to the positive level. The durations of generation of such output signals INT.sub.a1 and INT.sub.b1 are the basis of the fundamental frequency data of the string vibration. Regrettably, due to the influence of the overtone component included in the string vibration signal, these durations may not be the fundamental period of the string vibration. This influence of the overtone component is considered to some degree in designing pickup sensor 40-1 so as to reduce the influence (for instance, the function of detecting the occurrence of a zero cross in the opposite direction after the string vibration signal reaches its each peak). The removal of the remaining influence should be executed by microcomputer 30. That is, a pre-process for pitch extraction is executed by pickup sensor 40-1 and the final pitch extraction (period computation) is executed by microcomputer 30.

Pitch Extraction by Microcomputer (FIGS. 4A-4E, 5A and 5B)

In this embodiment, for the pitch extraction, microcomputer 30 employs the following basic conditions to accept the aforementioned signal generating duration (e.g., the generating duration of INT.sub.a1 or INT.sub.b1) as the fundamental period:

(i) Occurrence of a zero cross to the negative (positive) level after the string vibration signal reaches its positive (negative) peak,

(ii) Occurrence of a zero cross to the positive (negative) level after the string vibration signal reaches its negative (positive) peak after occurrence of the above zero cross (i), and

(iii) Occurrence of a zero cross to the negative (positive) level after the string vibration signal reaches its positive (negative) peak after occurrence of the above zero cross (ii).

Therefore, for instance, if INT.sub.a1 and INT.sub.b1 are alternately generated (i.e., if the positive and negative peaks are alternately generated), the INT.sub.a1 -generating duration t.sub.1 is evaluated as the fundamental period, so is the INT.sub.b1 -generating duration t.sub.2 (see FIG. 4E). However, if, after generation of signal INT.sub.a1, the same signal INT.sub.a1, not INT.sub.b1, is generated again, the INT.sub.a1 -generating duration is not evaluated as the reference period for the string vibration.

FIGS. 5A and 5B illustrate examples of the sequence for checking the above conditions. In the figures, INT.sub.a represents a signal generated upon occurrence of a zero cross after the positive peak of the vibration signal for each string is detected by the associated one of peak detectors 40-1 to 40-6. Similarly, INT.sub.b represents a signal generated upon occurrence of a zero cross after the negative peak of the vibration signal for each string is detected by the associated peak detector.

The flowcharts shown in FIGS. 5A and 5B are both executed as an interrupt process in microcomputer 30. Paying attention to the content of a flag, the flag is set to "1" at the first wave in the flow for the positive peak (FIG. 5A) and is reset to "0" at the first wave in the flow for the negative peak (FIG. 5B). The condition for executing the period computation in the flow for the positive peak is that the peak is not at the first wave (step B2) and the flag is set to "0," i.e., the negative peak has alr