51单片机c语言编写的播放乐曲程序+按键电子琴，通过按键可轮流选择要播放的乐曲！进入电子琴模式后，按下4*4矩阵键盘按键，将得到相应频率的发音！-51 single-chip player c language program+ key organ music through the buttons can take turns to choose to play music! Enter the organ mode, press t