Description
A method pioneered by Biz Markie is called a vocal tap.
Method
1. You hum and tap your throat just above your adams apple at the same time. The hum can be vocalised normally or done falsetto (high).
2. Open and close your mouth while you do the vocal tap to change the harmonics (tone) of the sound.
For more tutorials visit http://www.humanbeatbox.com/learn