please refer to fig4 . fig4 is a block diagram of a player 30 capable of vocal cancellation according to the present invention . the player 30 has a sound source circuit 32 , a signal module 34 , and two speaker modules 36 a , 36 b to play stereo sound . the sound source circuit 32 is a cd read mechanism , utilizing a read head 38 to read the signal data from a cd 40 , as well as processing the signal data to output each stereo signal li , ri . the signal module 34 is used to realize vocal cancellation of the present invention , outputting two output signals lo , ro having vocals cancelled according to two stereo signals li , ri . the signal module 34 has a mono processing module 50 and a low pass module 48 . to match two stereo signals li and ri , the signal module 34 also has two vocal cancellation modules 42 a , 42 b and two high pass modules 46 a , 46 b . the speaker modules 36 a , 36 b have individual d / a converters , power amplifiers , and speakers to transform the output signal lo , ro into acoustic waves . the process of vocal cancellation with the signal module 34 according to the present invention is described as follows . the mono processing module 50 of the signal module 34 can calculate the average of the stereo signals li , ri to generate a mono signal m , such that m =( li + ri )/ 2 . the present invention utilizes the mono signal m to perform vocal cancellation for each stereo signal . in the vocal cancellation module 42 a corresponding to the stereo signal li , the stereo signal li minus the mono signal m generates the mediate signal lvc ( lvc = li − m ). in the vocal cancellation module 42 b corresponding to the stereo signal ri , the difference of the stereo signal ri and the mono signal m generates the intermediate signal rvc ( rvc = ri − m ). as illustrated in fig2 , the vocal signal is usually mixed into the stereo signal with equal magnitude . in the present invention , the mono signal generated by the average of the stereo signals li , ri has the same vocals as that of each stereo signal . the present invention utilizes each vocal cancellation module corresponding to each stereo signal to subtract the mono signal from each stereo signal , individually performing vocal cancellation for each stereo signal . the difference from the prior art is that the present invention individually performs vocal cancellation according to each stereo signal , so the corresponding intermediate signals generated by different stereo signals after vocal cancellation are different . referring to the example of fig4 , the intermediate signal lvc of the stereo signal li after vocal cancellation is equal to li − m , and the other intermediate signal rvc of the stereo signal ri after vocal cancellation is equal to ri − m and is different from the intermediate signal lvc . as the discussed above , the stereo sound effect is caused by the difference of the stereo signals . in the present invention , the signal difference of the stereo sound effect generated by the stereo signals li and ri is preserved in the intermediate signals lvc and rvc . the present invention mainly utilizes the signal difference of the intermediate signals lvc and rvl to generate improved vocal - cancelled stereo sound compared to the prior art . note that in the prior technology of vocal cancellation shown as fig1 , the different stereo signals use the same vocal cancellation module to perform vocal cancellation with the same intermediate signal as the essential result of vocal cancellation . compared with the prior art , the present invention individually performs vocal cancellation according to the different stereo signals , which further preserves the signal difference of each stereo signal to better reproduce the stereo effect . as shown in fig4 , after generating the intermediate signals lvc and rvc according to the stereo signals li and ri , the signal module 34 can perform high - frequency and low - frequency compensation according to the intermediate signals lvc and rvc to generate the output signals lo and ro . the high pass module 46 a can extract the portion of the stereo signal li in the high - frequency band ( mainly the portion higher than the intermediate - frequency vocal band , please refer to fig2 and the related description ) as the high pass signal lh . the low pass module 48 can extract the portion of the signal s in the low - frequency band as the low pass signal s 1 . the signal s can be one of the stereo signals li and ri , or the mono signal m . mixing the high pass signal lh corresponding to the stereo signal li , the intermediate signal lvc , and the low pass signal s 1 with the mixing unit 52 a is equal to high and low - frequency compensation for the intermediate signal lvc , the mixing unit 52 a also generating the output signal lo corresponding to the stereo signal li ( lo = lvc + sl + lh ). in the same way , the high pass module 46 b can extract the portion of the stereo signal ri in the high - frequency band as the high pass signal rh , which allows high - frequency compensation for the intermediate signal rvc . mixing the high pass signal rh corresponding to the stereo signal ri , the intermediate signal rvc , and the low pass signal s 1 with the mixing unit 52 b is equal to high and low - frequency compensation for the intermediate signal rvc , the mixing unit 52 b also generating the output signal ro corresponding to the stereo signal ri ( ro = rvc + sl + rh ). please refer to fig5 . fig5 shows the spectrum of the output signals lo and ro generated by the operation of the signal module 34 according to the present invention . the horizontal axis in fig5 is frequency , and the vertical axis is magnitude . to continue the example in fig2 , if the spectrums of the stereo signals li , ri in fig4 are shown as the spectrums lf , rf in fig2 , the spectrums of the output signals lo , ro of the present invention are shown as the spectrums lof , rof in fig5 ( the spectrum rof is a dotted line and the spectrum lof is a solid line , and the frequencies fl , fh and the frequency bands bl , bm , bh in fig2 are also shown in fig5 ). in fig5 , the present invention individually performs vocal cancellation according to the different stereo signals , so the differences of the stereo signals distributed in the low - frequency band bl and the intermediate - frequency band bm are also preserved between the output signals lo and ro . this makes the output signals lo , ro of the present invention different not only in the high - frequency band bh but also in the low and intermediate - frequency bands . as a result , when the player 30 of the present invention outputs the output signals lo , ro with the speaker modules 36 a , 36 b , users can hear more abundant accompaniment with a more pronounced stereo sound effect and enjoy an improved accompaniment environment . each functional block of the signal module 34 of the present invention in fig4 can be implemented in the form of hardware , firmware , and / or software . for example , general players have programmable signal processing circuits , and the present invention can be implemented by firmware storing program code in the player memory . when the signal processing circuit executes such program code , vocal cancellation according to the present invention is effected . in addition , the present invention can be implemented to cancel vocals and offer background music in the form of software , such as the computer music playing programs , which usually cooperate with peripheral apparatuses ( such as sound cards and cd players ) to play music . please refer to fig6 . a program code 100 is used to implement vocal cancellation according to the present invention . the array variables x_l and x_r are used to represent the different stereo signals li and ri ( as in fig4 ), and the array variable mono represents the mono signal m . a subroutine hi_pass is used to implement the high pass modules , while a subroutine low_pass is used to implement the low pass modules . the array variables h_l and h_r individually represent the high pass signals lh and rh , the array variable low represents the low pass signal sl , and the array variables l_out and r_out individually represent the output signals lo and ro . the integer pointer j of program code 100 represents the j - th value of a variable array , and it also corresponds to the j - th sample of the corresponding signal of the variable array . shown in the program code 100 , the mono signal represented by the variable mono is the average of the variables x_l and x_r that correspond to each stereo signal , the high pass filtered results of the variables x_l and x_r are individually stored in the variables h_l and h_r . the stereo signal ri represented by the variable x_r is the signal s in fig4 , and the low pass signal sl generated by low pass filter is represented by the variable low . finally , the intermediate signals lvc and pvc are individually implemented by an operation x_l [ j ]− mono [ j ] and x_r [ j ]− mono [ j ] of the program code 100 . the sum of the intermediate signals , the variable of low - frequency compensation low , and the variables of high - frequency compensation h_l and h_r can generate the output signals of vocal cancellation according to the present invention , which are individually stored in the variables l_out and r_out . in vocal cancellation of the prior art , because the output signals of the different stereo channels use the same intermediate signal as the main result of vocal cancellation , the signal difference of the output signals in the low and mediate - frequency bands outside the high - frequency band is not clear to a listener . thus , the output signal of each stereo channel in the prior art does not produce a stereo sound effect of suitable quality . compared with the prior art , the present invention individually performs corresponding vocal cancellation according to the different stereo signals , so the output signal of each stereo channel preserves the whole signal difference . when the different speaker modules output the output signals , an improved stereo sound effect can be heard allowing users to better enjoy the accompaniment . in addition to typical cd players , the present invention can apply to other types of players , such as network modules that play music through a wired or wireless network . those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention . accordingly , that above disclosure should be construed as limited only by the metes and bounds of the appended claims .