In case you’re wondering what this colourful contraption is…. -it’s called a Pneumo Pro (Grumpy Cat not included!). It’s a plastic mock-up of the flute headjoint but with a series of propellors added.
One of the biggest problems with the flute is that you have little feel for what’s going on in this area, it’s all a bit abstract. The propellors will give a visual indication of where you’re actually blowing.
Beginners find it hard to get away from the instinct to blow directly down into the tube, meaning that little or no sound will happen. It’s only when the air stream is split across the leading edge of the embouchure hole that substantial tone will be generated.
For those attempting the second octave, here comes the next problem. So many will instinctively blow harder while still aiming at the same angle as for the lower octave. This, once again, gives a vivid picture of where it’s going wrong.
The simple/cheap version of this is to follow the example of Grumpy Cat and develop the overshot jawline, thus deflecting the airstream as required.