Another way to correct the mouth shape is to say "fish" or "two" in English.
At this time, your lips should not rest on your teeth, but should stretch forward a little.
If your lips are very dry, lick them before whistling.
2. Roll your tongue a little. Your tongue should be at the bottom of your mouth. You can help you put your tongue on the bottom by sticking it to your teeth, so that the edge of your tongue rolls up slightly. When you start whistling, you can make different sounds by changing the shape of your tongue.
For beginners, you can put your tongue on your lower teeth. Slowly, you can learn to control different sounds with your tongue.
3. Start blowing. Blow gently and slightly change the shape of lips and the curve of tongue until you can make a clear sound. This may take a few minutes, so don't give up too early.
Don't blow hard, blow gently. Once you find the correct position of your lips and tongue, you can make a louder sound.
When training, pay attention to keep your lips moist.
4. Make other whistles by changing the position of the tongue. Move your tongue forward slightly to whistle higher, and raise your tongue to whistle lower.
In order to produce bass, you should pay attention to keeping your chin in a relatively low position. To make a deep tone, you need to open your mouth.