请教一下51单片机矩阵键盘+蜂鸣器做电子琴的问题

#include<stc15.h>
#include<intrins.h>
#include<gpio.h>
#define uchar unsigned char
#define uint unsigned int
#define KEY P2     //矩阵键盘接口
sbit beep=P1^0;    //蜂鸣器
uchar key_volume=0;      //键值
uint code tone[14]={1276,1136,1012,956,852,759,716,638,568,506,57,51,45,43};   //音调分别为So(低)、La(低)、Si(低)、Do(中)、Re(中)、Mi(中)、Fa(中)、So(中)、La(中)、Si(中)、Do(高)、Re(高)、Mi(高)、Fa(高)

void Delay1ms()        //@11.0592MHz
{
    unsigned char i, j;

    _nop_();
    _nop_();
    _nop_();
    i = 11;
    j = 190;
    do
    {
        while (--j);
    } while (--i);
}

void Delayxms(uint t)
{
    uint x;
    for(x=0;x<t;x++)
    {
        Delay1ms();
    }
}

void Time0_init()      //定时器初始化
{
    TMOD=0x01;    //定时器0，方式1
    EA=1;
    ET0=1;
    TR0=1;
}

uchar keyscan()               //键盘扫描
{
    uchar row,colume;           //行、列变量
    KEY=0x0f;
    if(KEY!=0x0f)
    {   
        Delayxms(10);
        if(KEY!=0x0f)
        {
            KEY=0xef;
            if(KEY!=0xef)
            {
                row=0;
                goto colume_scan;
            }
        KEY=0xdf;
        if(KEY!=0xdf)
        {
            row=1;
            goto colume_scan;
        }
        KEY=0xbf;
        if(KEY!=0xbf)
        {
            row=2;
            goto colume_scan;
        }
        KEY=0x7f;
        if(KEY!=0x7f)
        {
            row=3;
            goto colume_scan;
        }
        return(16);

colume_scan:
        if((KEY&0x01)==0) colume=0;
            else if((KEY&0x02)==0) colume=1;
                else if((KEY&0x04)==0) colume=2;
                    else colume=3;
        key_volume=row*4+colume;
        while((KEY&0x0f)!=0x0f);
        }
    }
    else KEY=0xff;
    return(16);
}

void value_ISR() interrupt 1
{
    TF0=0;
    //keyscan();
    if(KEY==0xed)
    {
        TH0=(65536-tone[0])/256;        //填充初值
        TL0=(65536-tone[0])%256;
        TR0=1;
        beep=~beep;                    //发出不同音调
        while(KEY!=0xed);          //判断键释放
    }
    else if(KEY==0xeb)
    {
        TH0=(65536-tone[1])/256;
        TL0=(65536-tone[1])%256;
        TR0=1;
        beep=~beep;   
        while(KEY!=0xeb);   
    }
    else if(KEY==0xe7)
    {
        TH0=(65536-tone[2])/256;
        TL0=(65536-tone[2])%256;
        TR0=1;
        beep=~beep;   
        while(KEY!=0xe7);//判断键释放         
    }
    else if(KEY==0xde)
    {
        TH0=(65536-tone[3])/256;
        TL0=(65536-tone[3])%256;
        TR0=1;
        beep=~beep;        
        while(KEY!=0xde);   
    }
    else if(KEY==0xdd)
    {
        TH0=(65536-tone[4])/256;
        TL0=(65536-tone[4])%256;
        TR0=1;
        beep=~beep;        
        while(KEY!=0xdd);          //判断键释放
    }
    else if(KEY==0xdb)
    {
        TH0=(65536-tone[5])/256;
        TL0=(65536-tone[5])%256;
        TR0=1;
        beep=~beep;        
        while(KEY!=0xdb);   
    }
    else if(KEY==0xd7)
    {
        TH0=(65536-tone[6])/256;
        TL0=(65536-tone[6])%256;
        TR0=1;               
        beep=~beep;
        while(KEY!=0xd7);          //判断键释放
    }
    else if(KEY==0xbe)
    {
        TH0=(65536-tone[7])/256;
        TL0=(65536-tone[7])%256;
        TR0=1;               
        beep=~beep;
        while(KEY!=0xbe);   
    }
    else if(KEY==0xbd)
    {
        TH0=(65536-tone[8])/256;
        TL0=(65536-tone[8])%256;
        TR0=1;                    
        beep=~beep;
        while(KEY!=0xbd);          //判断键释放
    }
    else if(KEY==0xbb)
    {
        TH0=(65536-tone[9])/256;
        TL0=(65536-tone[9])%256;
        TR0=1;                    
        beep=~beep;
        while(KEY!=0xbb);   
    }
    else if(KEY==0xb7)
    {
        TH0=(65536-tone[10])/256;
        TL0=(65536-tone[10])%256;   
        TR0=1;
        beep=~beep;
        while(KEY!=0xb7);          //判断键释放
    }
    else if(KEY==0x7e)
    {
        TH0=(65536-tone[11])/256;
        TL0=(65536-tone[11])%256;
        TR0=1;
        beep=~beep;               
        while(KEY!=0x7e);   
    }
    else if(KEY==0x7d)
    {
        TH0=(65536-tone[12])/256;
        TL0=(65536-tone[12])%256;
        TR0=1;                    
        beep=~beep;
        while(KEY!=0x7d);          //判断键释放
    }
    else if(KEY==0x7b)
    {
        TH0=(65536-tone[13])/256;
        TL0=(65536-tone[13])%256;
        TR0=1;
        beep=~beep;               
        while(KEY!=0x7b);   
    }
}
void main()
{
    gpio();   //端口初始化
    Time0_init();
    while(1)
    {
        key_volume=0;      //键值清零
        keyscan();
        if(key_volume!=0 && key_volume!=15)
        {
            IE1=1;         //进入外部中断1   外部中断1可以这样触发吗
        }
    }
}