There is a simple pattern in the Beatbox. I rendered to a 2 bar wav and loaded it into the loop editor and used glide and non - glide notes to manipulate the loop.
While you could also chop up the loop, which has it's own benefits, there are also sonic advantages to this form of manipulation.
Edit: hit the play button and while the song plays press and hold the "Start" button of the PCMSynth to open the loop editor and view how the loop is being manipulated.
Soon I'll upload some examples to explain exactly how the loop editor behaves in case it's not apparent.