Is the whistle in The Future of Our Life blown with your mouth?

There are tools that can be blown out and blown to the mouth! However, "Our Days" should not be blown by mouth. If you blow with your mouth, it will not be so continuous and smooth. On the contrary, it will be brittle and there is no need to echo! How to prove this problem is not good! Wait until my heart aches-Jacky Cheung sings out of tune/but it looks like his MP3 single, but it doesn't feel like that!