The drag whistle is a high pitch whistle created by the tongue and the roof of your mouth. This sound was popularized by the likes of Beat Rhino and TylaDubya.
How it's done
- Get the tip of your tongue touch the back of the bottom row of your bottom teeth
- Have the middle section of your tongue touch the alveolar ridge (the place between your upper teeth and the roof of your mouth)
- Make sure there is some space in the back of your mouth and towards your throat
- Breathe in through a tiny gap between your tongue that's against the roof of your mouth
- At first, it'll come faintly, so practice and continue building that pressure and control
- Drink lots of water!
Video tutorial
https://youtu.be/Bz0MSUkZkLo