The Yamaha WX5 is like a pretend musical instrument that you can play by blowing into it.
It looks kind of like a long, skinny tube with keys on it, just like a regular musical instrument. But instead of using your hands to play the keys, you use your breath - that means you blow into it like a whistle.
When you blow into the WX5, it makes different sounds depending on which keys you press. You can change the sounds it makes by using a special machine that comes with it - kind of like changing the TV channel.
People like using the Yamaha WX5 because it lets them play music without having to use their hands - they can focus on their breath instead!