Patent Publication Number: US-9905209-B2

Title: Electronic keyboard musical instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Japanese Patent Application No. 2016-107716 filed on May 30, 2016 with the Japan Patent Office, and the entire disclosure of Japanese Patent Application No. 2016-107716 is incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to an electronic keyboard musical instrument. 
     As described, for example, in Japanese Unexamined Patent Application Publication No. 2015-184392, an electronic keyboard musical instrument is known in which, by depressing a damper pedal, when one or more keys are regularly pressed, resonant tones of the remaining keys that are not regularly pressed may be outputted. 
     SUMMARY 
     An acoustic piano comprises dampers (tone muting mechanisms that contact strings to stop string vibrations to thereby mute tones) each provided for a corresponding key. When a key is gently pressed to such an extent that a corresponding one of the dampers is raised, a resonant tone at a note of the gently pressed key is ready to be emitted. 
     In contrast, an electronic keyboard musical instrument having no damper has not been configured to output a resonant tone of any specific key selected from among all keys. Thus, when it is desired to output a resonant tone of a specific key using an electronic keyboard musical instrument, a pseudo resonant tone is outputted. 
     Specifically, in an electronic keyboard musical instrument, as a key pressing velocity is slower, a tone at a lower volume level is outputted; thus, a specific key of a note, at which a resonant tone is desired to be outputted, is regularly pressed at an extremely low speed to output an extremely small regular tone, thereby outputting a pseudo resonant tone of the specific key. 
     However, such an operation of regularly pressing a key at an extremely low speed is a quite delicate operation. Thus, when using an electronic keyboard musical instrument, a player cannot make a performance outputting a resonant tone of a specific key with a similar feeling of performance to that when playing an acoustic piano. 
     In the present disclosure, it is preferable to provide an electronic keyboard musical instrument that enables to output a resonant tone of a specific key with a similar feeling of performance to that when playing an acoustic piano. 
     An electronic keyboard musical instrument of the present disclosure comprises a detection sensor configured to detect a gentle key press, the detection sensor detecting that a key is gently pressed to an adjacent position that is shallower than and adjacent to a resonant performance position, the resonant performance position corresponding to a key press position to allow a damper to leave a string in an acoustic piano; a computer configured to, when the detection sensor detects a gentle key press to the adjacent position of at least one first key, among the plurality of keys, execute a resonance permission process to give a permission to output a resonant tone of the at least one first key; and a tone emission device configured to, when at least one second key different from the at least one first key and having a resonant relationship with the at least one first key is regularly pressed, emit a regular tone of the at least one second key and the resonant tone of the at least one first key. 
     As used herein, the term “regularly press a key” refers to an operation of regularly pressing a key so as to emit a tone, whereas the term “gently press a key” refers to an operation of gently pressing a key so as not to emit a tone. 
     With the above described configuration, when a key is gently pressed to the adjacent position shallower than the resonant performance position, a resonant tone of the key can be outputted individually; thus, the electronic keyboard musical instrument enables performance outputting a resonant tone of a specific key with a similar feeling of performance to that when playing an acoustic piano. 
     The electronic keyboard musical instrument of the present disclosure may comprise at least two key press sensors configured to detect a gentle key press at at least two different key press depth positions, in order to detect a key pressing velocity. In this case, at least one of the key press sensors that is configured to detect a gentle key press at the adjacent position shallower than the resonant performance position may be used as the detection sensor to detect a gentle key press at the adjacent position shallower than the resonant performance position. 
     With this configuration, it is possible to use the key press sensor for detecting a key pressing velocity as the detection sensor to detect a gentle key press to the adjacent position that is adjacent to the resonant performance position, and thus a simplified configuration of the electronic keyboard musical instrument can be achieved. 
     The computer in the electronic keyboard musical instrument of the present disclosure may be configured to, when the detection sensor detects a gentle key press of the at least one first key, set a resonant tone flag to give a permission to output the resonant tone of the at least one first key. In this case, the tone emission device may be configured to emit the resonant tone of the at least one first key for which the resonant tone flag is set. The electronic keyboard musical instrument with this configuration can easily emit a resonant tone by a flag process. 
     The electronic keyboard musical instrument of the present disclosure may be configured to execute a release determination process to determine whether the gentle key press of the at least one first key, for which the permission to output the resonant tone is given in the resonance permission process, is released; and a cancellation process, when it is determined in the release determination process that the gentle key press of the at least one first key is released, to cancel the permission in the resonance permission process for the at least one first key. 
     With such configuration, output of a resonant tone of a specific key can be stopped individually by a key release operation with a similar feeling to that when playing an acoustic piano. 
     The electronic keyboard musical instrument of the present disclosure may further comprise a sostenuto pedal, and may be configured such that the computer executes an operation determination process, when it is determined in the release determination process that the gentle key press is released, to determine whether an operation of the sostenuto pedal is performed before the gentle key press. Also, the electronic keyboard musical instrument may be configured such that the computer executes a cancellation suspension process, when it is determined in the operation determination process that the operation of the sostenuto pedal is performed, to suspend cancellation of the permission until the operation of the sostenuto pedal is released. 
     With such configuration, by performing a series of actions to gently press a specific key to an extent to allow output of a resonant tone, to depress the sostenuto pedal, and then to release the specific key in a similar manner as on an acoustic piano, the resonant tone of the specific key can be outputted even after releasing the specific key. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present disclosure will be described hereinafter by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram showing an internal configuration of an electronic piano according to the embodiment; 
         FIG. 2  is a flowchart of a main process; 
         FIG. 3  is a flowchart of a key event process; 
         FIG. 4  is a flowchart of a key press process; 
         FIG. 5  is a flowchart of a key release process; 
         FIG. 6  is a flowchart of a pedal event process; 
         FIG. 7  is a flowchart of a sostenuto pedal process; 
         FIG. 8  is a flowchart of a key damper flag process; 
         FIG. 9  is a flowchart of a regular tone output process; and 
         FIG. 10  is a flowchart of a resonant tone output process. 
     
    
    
     DETAILED DESCRIPTION 
     A description of an embodiment hereinafter shows only necessary configurations for convenience; however, this does not mean that an electronic piano  1  is configured only by these configurations. 
     As shown in  FIG. 1 , the electronic piano  1  of the present embodiment comprises a central controller  101  comprising a CPU  102 , a ROM  104 , and a RAM  106 . 
     The CPU  102 , the ROM  104 , the RAM  106 , and other devices are communicably coupled to one another through a system bus  100 . The CPU  102  communicates with the ROM  104 , the RAM  106 , and other devices through the system bus  100  to execute various processes as described later. 
     The ROM  104  comprises a program memory  104   a  that stores programs to be executed by the CPU  102 . 
     The RAM  106  temporarily stores flag information and other information generated when the CPU  102  executes the various processes. In the present embodiment, an SW 1  flag, an SW 2  flag, a tone emission flag, a key damper flag, a mute flag, and a pedal operation flag are stored in the RAM  106  so as to correspond to each of a plurality of keys  111 . 
     The electronic piano  1  comprises an operation panel  108 , a keyboard  110 , and a sostenuto pedal  112  as configurations of an operation system. 
     The operation panel  108  comprises a plurality of switches for setting various functions of the electronic piano  1 . The plurality of switches comprise, for example, a timbre switch to select a timbre of a tone. Operation information indicating that any of the switches is operated is outputted to the CPU  102 , and the CPU  102  executes the various processes in accordance with the operation information. 
     The keyboard  110  comprises eighty-eight keys  111 , and a key press sensor SW 1  and a key press sensor SW 2  are provided to each of the keys  111 . Each of the key press sensor SW 1  and the key press sensor SW 2  may be an optical sensor. The key press sensors SW 1 , SW 2  detect an operation (key press) of a corresponding one of the keys  111  at different depth positions. In the present embodiment, the key press sensor SW 1  is arranged at an adjacent position shallower than a resonant performance position that enables, in an acoustic piano, a damper to be raised to cause resonance of a string. Detection information outputted from the key press sensors SW 1 , SW 2  is outputted to the CPU  102  through the system bus  100 . 
     The sostenuto pedal  112  comprises a pedal sensor  112   a.  An operation of the sostenuto pedal  112  is detected by the pedal sensor  112   a,  and then detection information is outputted to the CPU  102 . The CPU  102  determines occurrence or non-occurrence of an operation of the sostenuto pedal  112  based on the detection information from the pedal sensor  112   a.  The pedal sensor  112   a  may be, for example, an optical sensor or may be another type of sensor. 
     The electronic piano  1  comprises, as a configuration to generate and output a tone, a regular tone generator  114 , a resonant tone generator  116 , an adder  118 , a DA converter  120 , and a sound system  122 . 
     The regular tone generator  114  is a tone generator, which comprises channels to be time division controlled in order to emit a plurality of tones simultaneously. The electronic piano  1  is capable of outputting a regular tone that is usually generated when a key  111  is regularly pressed and a resonant tone (a string resonance) that is generated when a string is caused to resonate with another string. The regular tone generator  114  is a device that is configured to generate regular tones. 
     The regular tone generator  114  comprises a tone waveform data memory (hereinafter, a “waveform memory”)  115 , and the waveform memory  115  stores waveform data (PCM waveform data, PCM: Pulse Code Modulation) representing respective pitches of the keys  111 , envelop data corresponding to key pressing velocities, and other data. 
     The regular tone generator  114  reads, from the waveform memory  115 , the waveform data of respective regular tones of keys  111  for each of which a tone emission flag is set in the RAM  106 , the envelop data stored in the RAM  106  and corresponding to velocity information of the respective keys  111  corresponding to the tone emission flags, and others. Then, the regular tone generator  114  assigns the read data (tone signals, such as the waveform data and the envelop data) to respective channels, and combines all tone signals assigned to the respective channels, and outputs the combined tone signals (in other words, regular tone signals) to the adder  118 . 
     The resonant tone generator  116  is also a tone generator, which is a device configured to generate resonant tones. 
     The resonant tone generator  116  comprises a tone waveform data memory (hereinafter, a “waveform memory”)  117 . The waveform memory  117  stores waveform data representing respective pitches of resonant tones that are to be emitted when respective strings of the keys  111  resonate in a case of an acoustic piano, and other data. 
     When a later-described SW 2  flag is set to a first key  111  (in other words, the first key  111  is regularly pressed), the resonant tone generator  116  reads, from the waveform memory  117 , waveform data of respective resonant tones of the second keys  111  which have resonant relationships with the first key  111  and for which key damper flags are set in the RAM  106 ; assigns the read waveform data (tone signals) to respective channels. The resonant tone generator  116  then combines all tone signals assigned to the respective channels; and outputs the combined tone signals (in other words, resonant tone signals) to the adder  118 . 
     The adder  118  adds resonant tones to a corresponding regular tone based on the regular tone signal and the resonant tone signals, and transmits the added tone signals for the added tones to the DA converter  120 . 
     The DA converter  120  converts the tone signals (digital signals) transmitted from the adder  118  to analog signals, and transmits the converted analog signals to the sound system  122 . 
     The sound system  122 , which comprises an amplifier, a speaker, and other components, externally outputs tones based on the analog signals transmitted from the DA converter  120 . 
     Next, descriptions will be given of the various processes, which are executed mainly by the CPU  102  of the electronic piano  1  configured as described above, with reference to flowcharts in  FIG. 2  to  FIG. 10 . 
     In the electronic piano  1 , when a power switch (not shown) is turned on, a main process shown in  FIG. 2  is executed. In the main process, an initialization process S 10  is executed, and then subsequent processes, i.e., a key event process S 20 , a pedal event process S 30 , a key damper flag process S 40 , a regular tone output process S 50 , and a resonant tone output process S 60 , are repeatedly executed in this order. 
     In the initialization process S 10 , a process of initializing the RAM  106 , the regular tone generator  114 , the resonant tone generator  116 , and other components is executed. Since the initialization process here is a general process, no further detailed description will be given. 
     In the key event process S 20 , specific processes shown in  FIG. 3  to  FIG. 5  are executed. In the key event process S 20 , a key press process S 210  ( FIG. 3 ,  FIG. 4 ) is a process that is executed when a key  111  is pressed. In the key event process S 20 , a key release process S 220  ( FIG. 3 ,  FIG. 5 ) is a process that is executed when a key  111  is released. If no key  111  is pressed or released, a negative determination (NO) is made in each of later-described steps S 21  to S 23 , and thus the key press process S 210  or the key release process S 220  is not executed. 
     As shown in  FIG. 3 , in the key event process S 20 , it is first determined whether a key press event has occurred (S 21 ). If a key is pressed, the key press is detected by the key press sensor SW 1  and the key press sensor SW 2  in this order (that is, in ascending order of key press depth). Specifically, in S 21 , it is determined whether the key press sensor SW 1  has detected a key press. If the key press sensor SW 1  has detected a key press, a corresponding detection signal is outputted to the CPU  102 . The CPU  102  determines in S 21  whether any detection signal is inputted from the key press sensor SW 1 . 
     If it is determined in S 21  that no detection signal indicating a key press of any key  111  is inputted (S 21 : NO), then S 22  is executed. If it is determined in S 21  that a detection signal is inputted (S 21 : YES), then the key press process in S 210  is executed. 
     In S 22 , it is determined whether a first key release event has occurred. When a key release is performed, the key release is detected by the key press sensor SW 2  and the key press sensor SW 1  in this order (that is, in descending order of key press depth). Specifically, in S 22 , it is determined whether the key press sensor SW 2  has detected a key release. If the key press sensor SW 2  has detected a key release, a corresponding detection signal is outputted to the CPU  102 . The CPU  102  determines in S 22  whether any detection signal is inputted from the key press sensor SW 2 . 
     If it is determined in S 22  that no detection signal indicating a key release of any key  111  is inputted (S 22 : NO), then S 23  is executed. If it is determined in S 22  that a detection signal is inputted (S 22 : YES), then the key release process in S 220  is executed. 
     In S 23 , it is determined whether a second key release event has occurred. In the present embodiment, a performance method as on an acoustic piano is available in which a resonant tone of a key is ready to be outputted by a gentle key press of the key to an extent where a corresponding damper leaves a string. In this case, the key press sensor SW 1 , which is arranged at the adjacent position shallower than the resonant performance position that is a key press position enabling the aforementioned performance method, detects the gentle key press; whereas, the key press sensor SW 2 , which is arranged at a deeper position than the resonant performance position, does not detect the gentle key press. In the case of such a gentle key press, it is not determined in S 22  that a key release has occurred, and thus it is determined in S 23  whether the key press sensor SW 1  has detected a key release in the present embodiment. 
     If it is determined in S 23  that no detection signal indicating a key release is inputted from the key press sensor SW 1  (S 23 : NO), the key event process S 20  is terminated, and the present process returns to the main process. If it is determined in S 23  that a detection signal is inputted (S 23 : YES), a process of resetting a later-described SW 1  flag is executed (S 230 ), and then the key event process S 20  is terminated, and the present process returns to the main process. 
     If it is determined in S 225  of the key release process S 220 , which will be described later, that a specified time has elapsed, and the processes beginning from S 20  are executed again, the same determination is not made in S 22  since it has been determined YES in the previous process in S 22  and the SW 2  flag is already reset in the subsequent process in S 221 . Specifically, it is not determined in the current process in S 22  that a key release has occurred based on resetting of the SW 2  flag. However, in subsequent S 23 , it may be determined that a key release has occurred based on an input of a detection signal indicating a key release from the key press sensor SW 1 . In such case, the process in S 230  is subsequently executed, and also processes of resetting a tone emission flag and setting a mute flag are executed in S 230  in place of the processes in S 224  and S 226 . 
     A description of the key press process S 210  will be given with reference to  FIG. 4 . When the key press process S 210  is started, a process of setting a SW 1  flag is first executed (S 211 ). One SW 1  flag for each key  111 , which is set or reset, is stored in the RAM  106 . 
     Next, a process is executed to start a timer for measuring a time to determine whether an operation that can be regarded as a gentle key press has been performed on a key  111  (S 212 ), and it is determined whether a detection signal is inputted indicating that the key press sensor SW 2  has detected a gentle key press within a specified time period measured by the timer (S 213 ). 
     If it is determined in S 213  that a detection signal is inputted from the key press sensor SW 2  (S 213 : YES), it is determined that a regular key press has occurred, and then S 214  is executed. Specifically, in S 214 , a process of setting an SW 2  flag of the key press sensor SW 2  is executed. One SW 2  flag for each key  111  is stored in the RAM  106 . 
     If it is determined in S 213  that no detection signal is inputted from the key press sensor SW 2  (S 213 : NO), then S 215  is executed. Specifically, in S 215 , a process is executed to determine whether a measured time by the timer started in S 212  has reached a specified time (i.e., whether the specified time has elapsed). 
     If it is determined in S 215  that the specified time has not elapsed (S 215 : NO), S 213  is executed again, and the processes from S 213  to S 215  are repeatedly executed until a regular key press is detected by the key press sensor SW 2  or the specified time has elapsed. 
     If it is determined in S 215  that the specified time has elapsed (S 215 : YES), the key press process S 210  is terminated, and the present process returns to the main process. 
     If the process of setting the SW 2  flag in S 214  is completed, a process of calculating a key pressing velocity (“velocity”) is executed in S 216 . Specifically, calculation is performed based on a time from a detection of the key press by the key press sensor SW 1  until a detection of the regular key press by the key press sensor SW 2 , which is a time from starting of the timer in S 212  until the determination in S 213  that a detection signal is inputted from the key press sensor SW 2  (S 216 ). 
     In S 216 , a process of setting a tone emission flag is also executed. One tone emission flag for each key  111  is stored in the RAM  106 . 
     When S 216  is completed, the key press process S 210  is terminated, and the present process returns to the main process. 
     A description of the key release process S 220  will be given with reference to  FIG. 5 . 
     When the key release process S 220  is started, a process of resetting the SW 2  flag of the key press sensor SW 2  is first executed (S 221 ). Specifically, the SW 2  flag for each key  111  is stored in the RAM  106  as described above, and the process in S 221  is executed to reset the SW 2  flag of the key press sensor SW 2  that has outputted the detection signal for the key  11  detected in S 22 . 
     Next, a process is executed to start a timer for measuring a time to determine whether an operation that can be regarded as a key release has been performed on the key  111  (S 222 ). It is determined whether a detection signal is inputted indicating that the key press sensor SW 1  has detected a key release within a specified time period measured by the timer (S 223 ). 
     If it is determined in S 223  that a detection signal is inputted from the key press sensor SW 1  (S 223 : YES), then S 224  is executed. Specifically, in S 224 , a process is executed to reset the SW 1  flag of the key press sensor SW 1  that has outputted the detection signal for the key  111  detected in S 22 . Also in S 224 , a process of resetting the tone emission flag set in S 216  (see  FIG. 4 ) is executed. 
     If it is determined in S 223  that no detection signal is inputted from the key press sensor SW 1  (S 223 : NO), then S 225  is executed. Specifically, in S 225 , a process is executed to determine whether a measured time by the timer started in S 222  has reached a specified time (i.e., whether the specified time has elapsed). 
     If it is determined in S 225  that the specified time has not elapsed (S 225 : NO), S 223  is executed again, and the processes from S 223  to S 225  are repeatedly executed until a regular key press is detected by the key press sensor SW 2  or the specified time has elapsed. 
     If it is determined in S 225  that the specified time has elapsed (S 225 : YES), the key release process S 220  is terminated, and the present process returns to the main process. 
     Meanwhile, when the process of resetting the SW 1  flag is completed in S 224 , then a process of setting a mute flag is executed in S 226 . One mute flag for each key  111 , which is set or reset, is stored in the RAM  106 . 
     When S 226  is completed, the key release process S 220  is terminated, and the present process returns to the main process. 
     Next, a description will be given of the pedal event process S 30 , which is executed subsequent to the key event process S 20  in the main process shown in  FIG. 2 , with reference to  FIG. 6 . 
     In S 30 , it is determined if any of a damper pedal (not shown), a soft pedal (not shown), and the sostenuto pedal  112  (shown in  FIG. 1 ) is operated. If it is determined that any of the pedals is operated, a damper pedal process S 310 , a soft pedal process S 320 , or a sostenuto pedal process S 330  corresponding to the operated pedal is executed. If it is determined that none of the pedals is operated, none of these pedal processes (S 310 , S 320 , S 330 ) is executed. 
     Hereinafter, a description will be given of the sostenuto pedal process S 330  executed when the sostenuto pedal  112  is operated with reference to  FIG. 7 . No detailed description will be given herein about any of the pedal processes (S 310 , S 320 ) executed when the damper pedal or the soft pedal is operated. 
     In the sostenuto pedal process S 330 , it is first determined whether the pedal sensor  112   a  has detected an operation of the sostenuto pedal  112  (S 331 ). 
     If it is determined in S 331  that the sostenuto pedal  112  is operated (S 331 : YES), then a process is executed to set a pedal operation flag for each of one or more keys  111  for each of which the SW 1  flag is set (S 332 ), and the sostenuto pedal process S 330  is terminated. 
     If it is determined in S 331  that the sostenuto pedal  112  is not operated (S 331 : NO), then it is determined in S 333  whether operation of the sostenuto pedal  112  is released. If it is determined in S 333  that operation of the sostenuto pedal  112  is released (S 333 : YES), then S 334  is executed. Specifically, in S 334 , a process of resetting the pedal operation flag for any of the keys  111  is executed, and then the sostenuto pedal process S 330  is terminated. If it is determined in S 333  that operation of the sostenuto pedal  112  is not released (S 333 : NO), the sostenuto pedal process S 330  is terminated immediately, and the present process returns to the main process. 
     Next, a description will be given of the key damper flag process S 40 , which is executed subsequent to the pedal event process S 30  in the main process shown in  FIG. 2 , with reference to  FIG. 8 . 
     As shown in  FIG. 8 , in the key damper flag process S 40 , a process is first executed to determine whether there is any key  111  for which the SW 1  flag of the key press sensor SW 1  is set (S 401 ). If it is determined in S 401  that there is any key  111  for which the SW 1  flag of the key press sensor SW 1  is set (S 401 : YES), then a process in S 403  is executed. If it is determined in S 401  that there is no key  111  for which the SW 1  flag of the key press sensor SW 1  is set (S 401 : NO), then a process in S 402  is executed. 
     The process executed in S 402  is to determine whether there is any key  111  for which the pedal operation flag is set. If it is determined in S 402  that there is any key  111  for which the pedal operation flag is set (S 402 : YES), then the process in S 403  is executed. If it is determined in S 402  that there is no key  111  for which the pedal operation flag is set (S 402 : NO), then a process in S 404  is executed. 
     The process executed in S 403  is to set key damper flags for all of the keys  111  for each of which it is determined in S 401  that the SW 1  flag of the key press sensor SW 1  is set, and for all of the keys  111  for each of which it is determined in S 402  that the pedal operation flag is set. When the process of setting the key damper flags is completed, then the key damper flag process S 40  is terminated, and the present process returns to the main process. 
     The process in S 404  is executed when it is determined in S 401  and S 402  that the SW 1  flag of the key press sensor SW 1  or the pedal operation flag is not set. In S 404 , if there are any keys  111  for each of which the key damper flag is set, then all of the key damper flags are reset, whereas if there is no key  111  for which the key damper flag is set, the process is simply terminated. When the process in S 404  is completed, then the key damper flag process S 40  is terminated, and the present process returns to the main process. 
     Next, a description will be given of a regular tone output process S 50 , which is executed subsequent to the key damper flag process S 40  in the main process shown in  FIG. 2 , with reference to  FIG. 9 . 
     As shown in  FIG. 9 , in the regular tone output process S 50 , it is first determined in S 501  whether a tone emission flag is newly set in the process of S 216  (see  FIG. 4 ). If it is determined that a tone emission flag is newly set (S 501 : YES), a process is executed to instruct the regular tone generator  114  to generate a new regular tone (S 502 ). 
     When the process in S 502  is executed, the regular tone generator  114  detects for which key  111  the new regular tone is instructed to be generated with reference to the RAM  106 , and outputs the new regular tone based on velocity information and others. 
     If it is determined in S 501  that no tone emission flag is newly set (S 501 : NO), then it is determined in S 503  whether there is any key  111  for which a mute flag is newly set in the process in S 226  (see  FIG. 5 ), that is, it is determined whether any key  111  is released. If it is determined that a mute flag is newly set (S 503 : YES), then a process is executed to instruct the regular tone generator  114  to mute a tone of the key  111  corresponding to the mute flag (S 504 ). 
     When receiving information to instruct muting, the regular tone generator  114  stops outputting the tone. Accordingly, thereafter, tones except the tone that is instructed to be muted are to be outputted from the regular tone generator  114 . 
     When the process in S 504  is completed, the mute flag is reset (S 505 ) and the regular tone output process S 50  is terminated, and then the present process returns to the main process. 
     Next, a description will be given of a resonant tone output process S 60 , which is executed subsequent to the regular tone output process S 50  in the main process shown in  FIG. 2 , with reference to  FIG. 10 . 
     In the resonant tone output process S 60 , it is first determined in S 601  whether any key damper flag is newly set in the process in S 403  (see  FIG. 8 ). If it is determined that a key damper flag is newly set (S 601 : YES), a process is executed to instruct the resonant tone generator  116  to generate a new resonant tone (S 602 ). 
     When the process in S 602  is executed, the resonant tone generator  116 , which stores the key damper flags for respective keys  111 , detects for which key  111  the key damper flag is newly set with reference to the RAM  106 , and also detects, with reference to the RAM  106 , whether there is any key  111  which has a resonant relationship with the key for which the key damper flag is newly set and which is regularly pressed (i.e., a key  111  for which the SW 2  flag is set). If there is any key  111  which has a resonant relationship and also is regularly pressed, a process is executed to instruct the resonant tone generator  116  to output a resonant tone of the key  111  for which the key damper flag is newly set. 
     If it is determined in S 601  that no key damper flag is newly set (S 601 : NO), then it is determined in S 603  whether there is any key damper flag newly reset in the process in S 404  (see  FIG. 8 ). That is, it is determined whether any key  111 , which is gently pressed without operation of the sostenuto pedal  112  so as to generate a resonant tone, is released, or whether operation of the sostenuto pedal  112  is finished. If it is determined that a key damper flag is newly reset (S 603 : YES), a process is executed to instruct the resonant tone generator  116  to stop emission of a resonant tone of the key  111  corresponding to the newly reset key damper flag (S 604 ). 
     When receiving information instructing to mute a resonant tone, the resonant tone generator  116  stops outputting the resonant tone. Accordingly, thereafter, resonant tones except the resonant tone instructed to be muted are generated by the resonant tone generator  116  and outputted by the sound system  122 . 
     When the process in S 604  is completed, the resonant tone output process S 60  is terminated, and the present process returns to the main process. 
     A description will now be given of characteristic operation and effects of the electronic piano  1  as described above. 
     According to the electronic piano  1  of the present embodiment, when a key  111  is gently pressed to the resonant performance position (a position between the key press sensor SW 1  and the key press sensor SW 2 ), it is possible to individually output a resonant tone of the gently pressed key  111 . Thus, the electronic piano  1  enables a performance to output a resonant tone of a specific key  111  with a similar feeling to that when playing an acoustic piano. 
     Also, according to the electronic piano  1  of the present embodiment, it is detected whether a key is gently pressed to the resonant performance position using the key press sensor SW 1  for detecting a key pressing velocity without separately providing a sensor for detecting whether a key is gently pressed to the resonant performance position. Thus, a simplified configuration of the electronic piano  1  can be achieved. 
     Further, according to the electronic piano  1  of the present embodiment, when a series of actions to gently press a specific key  111  to an extent to allow output of a resonant tone, to depress the sostenuto pedal  112 , and then to release the specific key  111  are performed in a similar manner as on an acoustic piano, the resonant tone of the specific key  111  can be outputted even after releasing the specific key  111 . Thus, the electronic piano  1  enables a performance to output a resonant tone of the specific key  111  by operating the sostenuto pedal  112  with a similar feeling to that when playing an acoustic piano. 
     Hereinafter is described one example of a correspondence relationship between the electronic piano  1  of the present embodiment and an electronic keyboard musical instrument of the present disclosure. 
     The electronic piano  1  of the present embodiment corresponds to one example of an electronic keyboard musical instrument of the present disclosure. 
     The key damper flag process executed by the CPU  102  of the present embodiment corresponds to one example of a resonance permission process of the present disclosure. 
     The key damper flag of the present embodiment corresponds to one example of a resonant tone flag of the present disclosure. 
     The resonant tone generator  116 , the adder  118 , the DA converter  120 , and the sound system  122  of the present embodiment correspond to one example of a tone emission device of the present disclosure. 
     The process in S 401  of the present embodiment corresponds to one example of a release determination process of the present disclosure. 
     The process in S 404  of the present embodiment corresponds to one example of a cancellation process of the present disclosure. 
     The process in S 402  of the present embodiment corresponds to one example of an operation determination process of the present disclosure. 
     The processes in S 401 , S 402 , and S 403  of the present embodiment correspond to one example of a cancellation suspension process of the present disclosure. 
     Other Embodiments 
     Although one embodiment has been described above, it is to be understood that the present disclosure is not limited to the aforementioned embodiment, but may be practiced in various forms. 
     (1) In the aforementioned embodiment, when a gentle key press of a key  111  is detected by the key press sensor SW 1 , it is determined that the key  111  is gently pressed to the resonant performance position. However, another sensor (a dedicated sensor may be employed) different from the key press sensor SW 1  may be provided to determine whether a key  111  is gently pressed to the resonant performance position. 
     (2) In the aforementioned embodiment, regular tones and resonant tones are outputted using a PCM method. However, a Digital Signal Processor (DSP) method may be employed instead. 
     (3) Although it is not particularly described in the aforementioned embodiment, there are no dampers for the highest notes in an acoustic piano. Thus, it may be configured such that, when determining whether any key damper flag is newly set (S 601 ), key damper flags are constantly set depending on a tone range even when both of the key press sensors SW 1  and SW 2  are “OFF.” 
     (4) In the aforementioned embodiment, when a gentle key press of a key  111  is detected by the key press sensor SW 1 , it is determined that the key  111  is gently pressed to the resonant performance position. A position of the key press sensor SW 1  may be varied depending on a desired timbre of a tone. 
     (5) Although the damper pedal is not specifically described in the aforementioned embodiment, it may be configured such that when the sostenuto pedal is depressed, the damper pedal is subsequently depressed (all strings are in a state of resonance), and then the damper pedal is released, the key damper flag is returned to an original state where the sostenuto pedal is depressed. 
     (6) Although one key press sensor SW 1  and one key press sensor SW 2  are provided for each key  111  in the aforementioned embodiment, a plurality of the key press sensors SW 1  and a plurality of the key press sensors SW 2  may be provided for each key  111 . 
     (7) Elements of the present disclosure are conceptual, and the present disclosure is not limited to the aforementioned embodiment. For example, a function served by one element may be dividedly assigned to a plurality of elements, or functions served by a plurality of elements may be integrally assigned to one element. Also, at least part of a configuration in the aforementioned embodiment may be replaced by a known configuration having a similar function. Further, at least part of a configuration in the aforementioned embodiment may be added to, or may replace, other configuration in the aforementioned embodiment.