Musical tone generating aparatus

The musical tone generating apparatus includes at least a waveform memory for storing waveform data, a stereophonic effect giving portion, left and right sound systems. The stereophonic effect giving portion gives stereophonic effect to the waveform data read from the waveform memory so that the left and right sound systems can generate left and right musical tones respectively based on the same waveform data outputted from the stereophonic effect giving portion. This stereophonic effect giving portion includes at least one digital filter whose filter coefficient can be adequately selected. This digital filter filters out the waveform data, and then the filtered waveform data are supplied to one of the left and right sound systems so that frequency characteristic of the left musical tone will be different from that of the right musical tone. Meanwhile, two digital filters can be provided at both inputs of the left and right sound systems.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a musical tone generating apparatus, and 
more particularly to a musical tone generating apparatus by which a 
technique for giving stereophonic effect can be improved. 
2. Prior Art 
As a conventional electronic musical instrument capable of demonstrating 
the stereophonic effect, the electronic musical instrument disclosed in 
Japanese Patent Laid-Open Publication No. 61-97698 is known. In this 
electronic musical instrument, a single tone performed by a non-electronic 
musical instrument (or acoustic musical instrument) such as a piano is 
picked up at its specific pick-up position, and then waveform data thereof 
are stored in a waveform memory by every pick-up tone. When tone pitch 
corresponding to the above-mentioned single tone is designated, the 
waveform data of plural tones are read from the waveform memory in 
parallel and then supplied to plural sound systems corresponding to the 
pick-up positions, so that plural pick-up tones can be simultaneously 
reproduced. 
According to the above-mentioned conventional technique, the waveform 
memory stores plural waveforms by single tone. For this reason, as number 
of the pick-up positions becomes large, data quantity to be stored must 
become enormous. Therefore, there is a disadvantage in that the waveform 
memory having large storage capacity or a plenty of waveform memories must 
be needed. 
SUMMARY OF THE INVENTION 
It is accordingly a primary object of the present invention to provide a 
musical tone generating apparatus by which the stereophonic effect can be 
obtained with relatively small memory capacity. 
In a first a aspect of the invention, there is provided musical tone 
generating apparatus comprising: 
(a) waveform memory means for storing several kinds of waveform data of 
musical tones to be generated in advance; 
(b) reading means for reading out desirable waveform data from the waveform 
memory means by desirable speed; and 
(c) stereophonic effect giving means for giving stereophonic effect to the 
desirable waveform data read from the waveform memory means so that left 
and right musical tones will be generated. 
In a second aspect of the invention, there is provided a musical tone 
generating apparatus comprising: 
(a) storing means for storing digitized waveform information concerning a 
musical tone; 
(b) reading means for reading the waveform information from the storing 
means by desirable speed; 
(c) first tone generating means for generating a first musical tone based 
on the waveform information read from the storing means; 
(d) digital filter means for inputting the waveform information read from 
the storing means; 
(e) second tone generating means for generating a second musical tone based 
on the waveform information outputted from the digital filter means at 
substantially same timing when the first musical tone is generated; and 
(f) control means for controlling a filter coefficient of the digital 
filter means so that frequency characteristic of the first musical tone 
will be different from that of the second musical tone. 
In a third aspect of the invention, there is provided a musical tone 
generating apparatus comprising: 
(a) storing means for storing digitized waveform information concerning a 
musical tone; 
(b) reading means for reading the waveform information from the storing 
means by desirable speed; 
(c) first and second digital filter means each inputting the waveform 
information read from the storing means; 
(d) first tone generating means for generating a first musical tone based 
on the waveform information outputted from the first digital filter means; 
(e) second tone generating means for generating a second musical tone based 
o the waveform information outputted from the second digital filter means 
at substantially same timing when the first musical tone is generated; and 
(f) control means for controlling filter coefficients of the first and 
second digital filter means so that frequency characteristic of the first 
musical tone will be different from that of the second musical tone.

DESCRIPTION OF A PREFERRED EMBODIMENT 
[A] Outline of the Invention 
The present invention relates to a musical tone generating apparatus which 
reads the waveform data from the waveform memory and then conducts such 
waveform data to plural sound systems to thereby generate musical tones in 
parallel. More specifically, a digital filter is arranged in a line of 
waveform data which is connected to at least one sound system. In this 
case, plural tones having different frequency characteristics are 
simultaneously generated based on waveform information of single tone. 
Therefore, coefficients of the digital filter are controlled so that 
frequency characteristics of the generated musical tones will be different 
from each other, i.e., plural tones will be accompanied with desirable 
stereophonic feelings. Thus, it is possible to obtain the stereophonic 
effect without storing the waveform information of plural tones which must 
be stored in the conventional apparatus, so that it is possible to reduce 
the memory capacity. 
[B] Circuit Constitution of Electronic Musical Instrument (FIG. 1) 
Next, detailed description will be given with respect to an embodiment of 
the present invention by referring to the drawings, wherein like reference 
characters designate like or corresponding parts throughout the several 
views. In FIGS. 1 to 3 and FIGS. 6 to 8, a signal line added with an 
oblique line "/" (such as a signal line of "KC" shown in FIG. 1) may 
include plural signal lines or designate flow of a signal of plural bits. 
FIG. 1 shows the circuit constitution of the electronic musical instrument 
according to an embodiment of the present invention. This electronic 
musical instrument is designed so that plural tones can be simultaneously 
generated by time division process of plural channels (e.g., eight 
channels). 
In FIG. 1, plural keys of a keyboard 12 are divided into some key groups 
each including half octave keys (i.e., six keys), and a waveform memory 10 
stores the waveform data corresponding to one key representing each key 
group. In the present embodiment, the waveform memory 10 stores such 
waveform data of some key-touch intensity levels (e.g., three levels 
indicative of weak, middle and strong key-touch intensities). The reason 
why the waveform data are stored by every key group as described above is 
to enable key scaling control so that tone color and the like can be 
differed in response to each key group. In addition, the reason why the 
waveform data are stored by every key-touch intensity level is to enable 
touch response control so that the tone color, tone volume and the like 
can be differed in response to the key-touch intensity level. Further, the 
waveform memory 10 stores the waveform data representative of performance 
tones of piano (as non-electronic musical instrument), for example. 
Detailed description concerning the method for storing such waveform data 
will be described later. 
A key-depression detecting/tone-generation assigning circuit 14 detects a 
depressed key within the keyboard 12 and then assigns key code data KC 
(representative of a key code or tone pitch of the detected key) and a 
key-on signal KON (representing that there exists the depressed key) to a 
vacant channel thereof. These data are outputted by a timing of such 
assigned vacant channel. 
A touch detecting circuit 16 detects which of the weak, middle and strong 
key-touch intensity levels (or touch levels) the depressed key within the 
keyboard 12 corresponds to. Then, the touch detecting circuit 16 outputs 
touch level data TD indicative of the detected touch level in synchronism 
with the timing of the channel to which the above-mentioned data KC and 
signal KON are assigned. 
As described above, these two circuits 14 and 16 operate based on the time 
division system, hence, latter circuits connecting to and responding to 
the outputs of these circuits also operate based on the time division 
system. In the following description, description will be given with 
respect to the operation of only one channel for convenience. 
A waveform selecting circuit 18 generates waveform designating data WS in 
response to the key code data KC and the touch level data TD. In response 
to this waveform designating data WS, the waveform data to be read from 
the waveform memory 10 are designated. For example, when the key code 
indicated by the key code data KC belongs to a first key group, the 
waveform data corresponding to the touch level indicated by the touch 
level data TD are read out and designated from several waveform data 
corresponding to this first key group. 
An address generating circuit 20 generates an address signal AD in response 
to the key code data KC and the key-on signal KON. In accordance with this 
address signal AD, the waveform data designated by the waveform 
designating data WS are read from the waveform memory 10. In this case, 
such address designation by the address signal AD is executed at a speed 
corresponding to the key code (or tone pitch) indicated by the key code 
data KC. Thus, the tone pitch of the generated musical tone is determined 
in response to reading speed at this time. Meanwhile, plural keys belongs 
to the same one key group, however, the same waveform data are read out by 
every key at different reading speed in the case where the keys in one key 
group are depressed by constant touch level. 
An envelope giving circuit 22 gives an amplitude envelope to waveform data 
WD read from the waveform memory 10. This envelope giving circuit 22 is 
constituted by an envelope generator and a multiplier. The envelope 
generator generates envelope waveform data indicative of the envelope 
whose level rises up in response to the key-on signal KON and then 
attenuates, for example. The multiplier multiplies the generated envelope 
waveform data by the waveform data WD. In this case, the key code data KC 
and the touch level data TD are used for determining envelope 
characteristics such as attack time, attack level, decay time and the 
like. As the above-mentioned envelope generator, it is possible to adopt 
an envelope generator which includes an envelope memory and a reading 
circuit. This envelope memory stores the envelope waveform data 
corresponding to each waveform data pre-stored in the waveform memory 10. 
The reading circuit reads the envelope waveform data designated by the key 
code data KC and the touch data TD from the envelope memory. According to 
needs, it is possible to adopt a digital operation type envelope 
generator. 
The above-mentioned envelope giving circuit 22 outputs waveform data EWD, 
which are supplied to a sound system 24L for left channel and also 
supplied to a sound system 24R for right channel via a digital filter 26. 
Both of the sound systems 24L and 24R generate musical tones based on the 
supplied waveform data. As known well, such sound system can be 
constituted by use of an accumulator, a digital-to-analog (D/A) converter, 
an amplifier and a speaker etc., for example. 
A coefficient selecting circuit 28 selects and reads out one of many filter 
coefficients stored in a filter coefficient memory 30. More specifically, 
this coefficient selecting circuit 28 selectively reads out the filter 
coefficient in response to a frame address signal FAD constituted by 
upper-bit signal of the address signal AD, the key code data KC and the 
touch level data TD. 
The filter coefficient memory 30 stores the filter coefficients of plural 
frames by every waveform data stored in the waveform memory 10, but 
description concerning the storing method and reading operation thereof 
will be given later. 
The filter coefficient read from the filter coefficient memory 30 is 
supplied to the digital filter 26, which is constituted by the known FIR 
digital filter or IIR digital filter. This digital filter 26 controls to 
vary spectrum distribution of the waveform data EWD in response to the 
supplied filter coefficient. 
[C] Musical Tone Waveform Storing Unit (FIG. 2) 
FIG. 2 shows the musical tone waveform storing unit which is used when the 
waveform memory 10 stores the waveform data in the above-mentioned 
electronic musical instrument. 
In the vicinity of a piano 40, right microphone 42R and left microphone 42L 
are provided in order to pick up the performance tone of the piano 40. 
Tone signal picked up by the right microphone 42R has a waveform as shown 
in FIG. 4, for example. This tone signal is supplied to an 
analog-to-digital (A/D) converter 44R wherein pick-up tone waveform is 
sampled by predetermined time interval and an amplitude value at each 
sample point is converted into digital data. Such digital data are 
sequentially supplied to a waveform memory 46R as the waveform data. Thus, 
the waveform data corresponding to the pick-up tone are written into the 
waveform memory 46R under control of a writing control circuit 48. 
Similarly, the tone signal picked up by the left microphone 42L is 
converted into the waveform data by an A/D converter 44L, and then such 
waveform data are written into a waveform memory 46L under control of the 
writing control circuit 48. After all, the musical tone waveform storing 
unit shown in FIG. 2 works as a pulse code modulation (PCM) recording unit 
of two channels (i.e., left and right channels). 
In the actual recording, the keys within the piano 40 are subjected to 
grouping in response to the key groups of the keyboard 12 shown in FIG. 1. 
One key representing each key group is depressed by different touch levels 
(i.e., weak, middle and strong touch levels) so that piano tones are 
generated. As a result, the waveform memory 46R stores right pick-up tone 
waveforms corresponding to three touch levels by each key group. 
Similarly, the waveform memory 46L stores left pick-up tone waveforms 
corresponding to three touch levels by each key group. 
The waveform data stored in &he waveform memory 46L for left channel are 
transferred and then stored in the waveform memory 10 shown in FIG. 1. In 
this case, the waveform between rising point and middle of attenuating 
portion of each pick-up tone waveform is divided into N frames (where one 
frame is set as 10 msec, for example) such as divisions C.sub.l to C.sub.N 
along time axis of the graph shown in FIG. 4. The waveform data 
corresponding to the divisions C.sub.l to C.sub.N are stored in the 
waveform memory 10, but the waveform data corresponding to the attenuating 
portion of the waveform after the division C.sub.N are not stored in the 
waveform memory 10. Thus, when the waveform data are read from the 
waveform memory 10, the waveform data corresponding to the division 
C.sub.N are repeatedly read out after such waveform data are read out. 
Incidentally, when the waveform data are stored in the waveform memory 10, 
it is possible to store the waveform data which are obtained by 
standardizing the amplitude level of each pick-up tone waveform to a 
constant level L.sub.O such as the maximum level and the like, for 
example. Thus, it is possible to digitize the amplitude value in lower 
amplitude portion of the waveform with. In this case, there is no problem 
occurred due to the above-mentioned standardization because the envelope 
giving circuit 22 gives the amplitude envelope to the waveform data as 
described before. 
[D] Filter Coefficient Writing Unit (FIG. 3) 
FIG. 3 shows the filter coefficient writing unit which is used when the 
filter coefficients are stored in the filter coefficient memory 30 in the 
electronic musical instrument shown in FIG. 1. In FIG. 3, the waveform 
data have been already written into the waveform memories 46R and 46L as 
described in FIG. 2. The waveform data corresponding to the divisions 
C.sub.l to C.sub.N are read from each waveform memory by each pick-up tone 
waveform under control of a reading control circuit 50. The waveform data 
read from each of the waveform memories 46R and 46L are supplied to each 
of spectrum analysis circuits 52R and 52L. 
Each of the spectrum analysis circuits 52R and 52L effects the spectrum 
analysis on each of the frames C.sub.l to C.sub.N by each pick-up tone 
waveform to thereby output spectrum analysis outputs S(R) and S(L) 
respectively, both of which are supplied to a differential operation 
circuit 54. 
Each of FIGS. 5A to 5C shows an example of spectrum analysis of one frame. 
The spectrum analysis circuit 52R effects the spectrum analysis on the 
right pick-up tone waveform of one frame to thereby generate the spectrum 
analysis output S(R) as shown in FIG. 5A, while the spectrum analysis 
circuit 52L effects the spectrum analysis on the left pick-up tone 
waveform of one frame to thereby generate the spectrum analysis output 
S(L) as shown in FIG. 5B. 
The differential operation circuit 54 subtracts the spectrum analysis 
output S(R) from the spectrum analysis output S(L) by each frame to 
thereby generate a differential spectrum output S(L-R) which corresponds 
to the differential of two outputs S(L) and S(R). This differential 
spectrum output S(L-R) is supplied to a filter coefficient operation 
circuit 56. S(L-R) shown in FIG. 5C designates an example of the 
difference spectrum output between the spectrum analysis outputs S(L) and 
S(R). 
The filter coefficient operation circuit 56 calculates out the filter 
coefficient based on the differential spectrum output S(L-R) by each 
frame. Then, the calculated filter coefficient is written into the filter 
coefficient memory 30. 
The filter coefficient memory 30 provides storing areas 30A of (key group 
number).times.(touch level number, i.e., three in the present embodiment), 
each of which includes N storing portions in order to write the filter 
coefficients respectively corresponding to the frames C.sub.l to C.sub.N 
therein. As described above, the spectrum analysis and the filter 
coefficient operation are effected on one pair of left and right pick-up 
tone waveforms by every frame, so that the filter coefficients of N frames 
can be stored in each storing area 30A. 
In order to read the filter coefficients from the filter coefficient memory 
30, the coefficient selecting circuit 28 designates the storing area to be 
read out in response to the key code data KC and the touch level data TD. 
Then, the filter coefficients corresponding to the frames C.sub.l to 
C.sub.N are sequentially read from the designated storing area in response 
to the frame address signal FAD. In this case, this frame address signal 
FAD is constituted by upper-bit signal within the address signal AD. When 
the address signal AD designates the address of the waveform of specific 
frame, the address of the filter coefficient corresponding to this 
specific frame is designated. As a result, while the waveform data of the 
frame C.sub.l are read out, the filter coefficient corresponding to this 
frame C.sub.l is read from the filter coefficient memory 30 and then 
supplied to the digital filter 26, for example. 
Therefore, in accordance that the waveform data indicative of the left 
pick-up tone waveform are read from the waveform memory 10, the filter 
coefficients corresponding to the frames C.sub.l to C.sub.N are 
sequentially supplied to the digital filter 26. Thus, the waveform data 
passing through the digital filter 26 are given with the spectrum 
distribution similar to that of the right pick-up tone waveform by each 
frame. As a result, the musical tones generated from the sound systems 24L 
and 24R will perform the stereophonic effect. 
In the above description, the lengths of the frames C.sub.l to C.sub.N are 
set equal to each other. However, it is possible to set these frame 
lengths different from each other. In the case where the frame lengths are 
set different from each other, it is necessary to provide a frame address 
generating circuit 27 which inputs the address signal AD and then 
generates the frame address signal FAD as shown by dotted line in FIG. 1. 
This frame address generating circuit 27 compares the address signal AD to 
end address of waveform data by each frame. At every time when it is 
detected that the address signal AD coincides with the end address of 
waveform data, this circuit 27 generates the frame address signal FAD so 
as to designate the next frame. 
[E] Another Example of Stereophonic Effect Giving Portion (FIG. 6) 
FIG. 6 shows another example of the stereophonic effect giving portion. In 
FIG. 6, parts identical to those shown in FIG. 1 are designated by the 
same numerals, hence, detailed description thereof will be omitted. 
The features of the circuit shown in FIG. 6 are that a digital filter 26R 
is arranged between the envelope giving circuit 22 and the sound system 
24R while a digital filter 26L is arranged between the envelope giving 
circuit 22 and the sound system 24L. The filter coefficients are supplied 
to the digital filter 26R from the filter coefficient memory 30R which is 
controlled by the coefficient selecting circuit 28R, while the filter 
coefficients are supplied to the digital filter 26L from the filter 
coefficient memory 30L which is controlled by the coefficient selecting 
circuit 28L. The coefficient selecting circuits 28R and 28L work similar 
to the coefficient selecting circuit 28 shown in FIG. 1. In addition, the 
filter coefficient memories 30R and 30L are identical to the filter 
coefficient memory 30 shown in FIG. 1. 
The data different from that in FIG. 1 are stored in the waveform memory 
10, the filter coefficient memories 30R and 30L shown in FIG. 6. As the 
unit for generating such data to be stored, it is possible to use the 
units shown in FIGS. 7 and 8. 
[F] One Example of Data Generating Unit (FIG. 7) 
In the data generating unit shown in FIG. 7, the waveform memories 46R and 
46L, the reading control circuit 50, the spectrum analysis circuits 52R 
and 52L are similar to those shown in FIG. 3. 
An adder circuit 60 adds the waveform data (corresponding to the right 
pick-up tone) read from the waveform memory 46R to the waveform data 
(corresponding &o the left pick-up tone) read from the waveform memory 46L 
by every corresponding sample point. Through this adding operation, it is 
possible to obtain combined waveform data of left and right pick-up tones, 
which are written into the waveform memory 10. Similar to the case 
described in FIG. 2, the data actually written into the waveform memory 10 
are the waveform data of N frames C.sub.l to C.sub.N in this case. 
A filter coefficient operation circuit 56R calculates out the filter 
coefficients based on the spectrum analysis output S(R) outputted from the 
spectrum analysis circuit 52R. These calculated filter coefficients are 
written into the filter coefficient memory 30. On the other hand, a filter 
coefficient operation circuit 56L calculates out the filter coefficients 
based on the spectrum analysis output S(L) outputted from the spectrum 
analysis circuit 52L, and the calculated filter coefficients are written 
into the filter coefficient memory 30L. 
By effecting the spectrum analysis and filter coefficient operation on the 
left and right pick-up tone waveforms by every frame, the filter 
coefficient memory 30R stores the filter coefficients of N frames 
concerning the right pick-up tone waveform, while the filter coefficient 
memory 30L stores the filter coefficients of N frames concerning the left 
pick-up tone waveform. Such filter coefficient storing process is 
performed by each combined waveform data to be stored in the waveform 
memory 10. 
Thereafter, the waveform memory 10, the filter coefficient memories 30R and 
30L which store &he data as described above are used and applied to the 
circuit shown in FIG. 6. When this circuit shown in FIG. 6 is operated, 
the spectrum distribution corresponding to the right pick-up tone can be 
obtained at output side of the digital filter 26R, while another spectrum 
distribution corresponding to the left pick-up tone can be obtained at 
output side of the digital filter 26L. Therefore, the musical tones 
generated from the sound systems 24R and 24L can have the stereophonic 
effect. 
[G] Another Example of Data Generating Unit (FIG. 8) 
In the data generating unit shown in FIG. 8, parts similar to those shown 
in FIG. 7 will be designated by the same numerals. 
The data generating unit shown in FIG. 8 is different from that shown in 
FIG. 7 in that a spectrum analysis circuit 62, differential operation 
circuits 64L and 64R are provided. This spectrum analysis circuit 62 
effects the spectrum analysis on the inputted waveform data (indicative of 
the combined waveform of the left and right pick-up tones), the 
differential operation circuit 64L subtracts the spectrum analysis output 
S(R) of the spectrum analysis circuit 52R from the spectrum analysis 
output S(L+R) of the spectrum analysis circuit 62, and the differential 
operation circuit 64R subtracts the spectrum analysis output S(L) of the 
spectrum analysis circuit 52L from the above spectrum analysis output 
S(L+R). In addition, the filter coefficient operation circuit 56L 
calculates out the filter coefficient based on output S(L+R)-S(R) of the 
differential operation circuit 64L, and then the calculated filter 
coefficient is written in the filter coefficient memory 30L. On the other 
hand, the filter coefficient operation circuit 56R calculates out the 
filter coefficient based on output S(L+R)-S(L) of the differential 
operation circuit 64R, and then the calculated filter coefficient is 
written in the filter coefficient memory 30R. The other constitution in 
the unit shown in FIG. 8 is similar to that in the unit shown in FIG. 7. 
FIG. 9 shows an example of spectrum analysis of one frame in the unit shown 
in FIG. 8. The output S(L+R) of the spectrum analysis circuit 62 
designates the spectrum distribution corresponding to the sum of the 
spectrum distribution indicated by the output S(L) of left pick-up tone 
and the spectrum distribution indicated by the output S(R) of right 
pick-up tone. In addition, the output S(L+R)-S(R) of the differential 
operation circuit 64L designates the spectrum distribution approximately 
identical to the spectrum distribution indicated by the output S(L) of 
left pick-up tone, while the output S(L+R)-S(L) of the differential 
operation circuit 64R designates the spectrum distribution approximately 
identical to the spectrum distribution indicated by the output S(R) of 
right pick-up tone. 
Therefore, when the circuit shown in FIG. 6 is operated by use of the 
waveform memory 10, the filter coefficient memories 30R and 30L in which 
respective data are stored by the unit shown in FIG. 8, the musical tones 
generated from the sound systems 24R and 24L can perform the stereophonic 
effect similar to the case where the data are stored in the above memories 
by the unit shown in FIG. 7. 
[H] Modified Example 
The present invention is not limited to the above-mentioned embodiments, so 
that it is possible to enforce the present invention by several 
modifications. For example, the following modifications can be considered: 
(1) As the method for storing and reading the musical tone waveform, the 
method disclosed in Japanese Patent Laid-Open Publication No. 60-147793 
can be applied to the present invention, for example. In this case, the 
waveform memory stores plural cycle waveforms of attack portion and 
continuing segment waveforms (i.e., partial waveforms). After plural cycle 
waveforms of attack portion are read out, the segment waveforms are read 
out with executing smooth interpolation. 
(2) As the method for recording and reproducing the musical tones, some 
data compression methods can be applied to the present invention. For 
example, it is possible to adopt the Differential Pulse Code Modulation 
(DPCM) method, Adaptive Differential Pulse Code Modulation (ADPCM) method, 
Delta Modulation (DM) method, Adaptive Delta Modulation (ADM) method, 
Linear Predictive Coding (LPC) method and the like. Or, it is possible to 
adopt the combined method of some of above methods, such as the combined 
method of LPC and ADPCM methods, for example. 
(3) As the method for controlling touch response and key scaling, it is 
possible to adopt the method disclosed in Japanese Patent Laid-Open 
Publication No. 60-52895 in which the data read from the waveform memory 
are processed by the digital filter or another method disclosed in 
Japanese Patent Laid-Open Publication No. 60-55398 in which combining 
ratio between two data respectively read from two waveform memories are 
controlled. 
(4) In the present embodiments, the waveform data selected by the waveform 
selecting circuit 18 are read out in response to the address signal from 
the address generating circuit 20. However, it is possible to modify the 
address generating circuit 20 to have the function of waveform selecting 
circuit 18. 
(5) The present invention can be applied to single tone electronic musical 
instrument, sampling electronic musical instrument, rhythm electronic 
musical instrument and the like. 
(6) The present embodiments relate to the case where the tone color is 
represented by the piano tone. However, it is possible to enforce the 
present invention by using other tone colors. 
(7) The filter coefficient is varied in lapse of time in the present 
embodiments. However, it is possible to select and use one representative 
filter coefficient. 
(8) The number of sound systems is not limited to two sound systems for 
left and right pick-up tones. It is possible to provide further more sound 
systems. 
(9) It is possible to combine the musical tone signals of left and right 
channels so as not to damage the stereophonic effect. 
(10) The frame change-over control is performed by use of the address 
signal in the present embodiments. However, it is possible to perform this 
frame change-over control by use of time information. 
Above is description of preferred embodiments. This invention may be 
practiced or embodied in still other ways without departing from the 
spirit or essential character thereof as described heretofore. Therefore, 
the preferred embodiments described herein are illustrative and not 
restrictive, the scope of the invention being indicated by the appended 
claims and all variations which come within the meaning of the claims are 
intended to be embraced therein.