This extensive MRI study of the various sounds, produced by one 27-year-old beatboxer, has found the same mechanisms used in human speech and breathing were exploited for the polyphonic beatboxing, in which the percussion, a bass line, and vocals are produced.
The research team, consisting of Michael Proctor, Shirkanth Narayanan, and Krishna Nayak, are to begin investigating this further, including the patterns of articulation that do not occur in the phonologies of the artist's native languages. Example, some of the sounds resembled the clicks in some South African tribes.
Take a look at the likes of the "808 kick" and "breathy hi-hat" in the source link below.
Source: USC SPAN