Your beatbox performance must have at least three levels going on at the same time: low, middle and high sounds. If you want to improve your beatboxing skills, you have to practice keeping all three levels going simultaneously. To do this, practice each level by itself. After you can make the sounds without thinking about them, you can start putting them together so that they sound like you are doing them at the same time.
Sing a high synthesizer sound using your falsetto voice. This is the voice above your normal range that sounds thin and bird-like. Find it by singing up the scale until you get too high for your regular voice. Switch to falsetto to go higher. You will feel the vibration in the top of your mouth instead of down in your throat where you feel your regular voice. Now make a synthesizer melody using your falsetto with short notes that sound like “do.” Put them together in a regular pattern, such as “do-do-do-do,” sung on the beat.
Press your lips together and blow air through them to make a lip vibration. Make a note in your regular voice as you do this. It will sound a little like blowing bubbles or a motor-boat sound. This sound doesn’t usually have a melody. It is used to add to the percussion effect of beatboxing.
Create rhythms that are syncopated. Syncopation is when you use your kick and snare sounds produced by the throat and tongue in unusual places. Instead of doing the kick on the first beat and the snare on the third, do them in unusual places to make a beat that goes out of the pattern temporarily.
Put all the sounds together. Start with your synthesizer sound. Make a melody with your falsetto voice and the “do” syllables. Add in your kick and snare sound on the first and third beats. Because your falsetto is a singing voice and the kick and snare are percussion sounds made by blowing air through your lips or swallowing, you can make them at the same time. Practice making kick and snare sounds while you sing your synthesizer line. Add in some sound effects by throwing in a lip vibration. This will interrupt the synthesizer melody for one beat, but your listener won’t pay attention to that. Move your kick and snare to the second and fourth beats for a quick syncopation. Come back to the first and third beats and produce the original melody. Putting synthesizer sounds, lip vibrations and syncopation in your beatbox vocals will improve your skills dramatically.