用短时傅立叶变换方法实现歌曲变调功能，变调最小步长为1个半音

此效果为模拟音讯的升降KEY,其中程式码14行的pit_ratio为升降系数大于1为升KEY小于1为降KEY -This effect is to simulate the movements of audio KEY, in which the code 14 for the lift coefficient of the line pit_ratio greater than 1 is less than 1 liter KEY to drop KEY

音频变调不变速算法处理，效果较好，但是计算稍微有点复杂，分享出来。有兴趣的同学可以进一步改进(Audio variable-speed algorithm processing, the effect is better)