基于AT89C51的音乐倒数计数器，倒计时的时间可以通过按键来实现加减，倒计时的时间到后，蜂鸣器发出一段音乐进行报警提示，同时LED灯点亮-Based on AT89C51 music countdown counter, countdown time can be achieved through the key addition and subtraction, the countdown to the time after the buzzer alarm some music while LED lights