This short video illustrates how the human larynx produces voice and different pitches.

The vocal folds are capable of very rapid vibration. As air escapes the larynx and passes the vibrating vocal "cords," their movement is imparted to the escaping air, and is transmitted as "voice." Slower cord vibrations produce lower pitches, while more rapid vibrations lead to higher pitched tones.

The musculo-cartilaginous structure of the larynx is exceedingly complex and can produce precise and extremely rapid motions of the vocal cords.