This instrument creates a Shepard tone.
See http://en.wikipedia.org/wiki/Shepard_tone for more info on what a Shepard tone is.

p-fields:

p4 is the pitch or frequency

p5 is the amplitude

BSB widgets:

speed is how fast each component varies

envelope shape determines when the amplitude of a component is the highest,
more to the beginning or to the end; use 0.5 for regular Shepard tone

pulse width is used for the vco2 opcode if the waveform is square or triangle,
values are limited to the stable range

speed, envelope shape, pulse width and panning have an extra text field
which in the code is appended to the value of the knob;
use e.g. *p6 to change the value from the score

For a regular Shepard tone, use a sine wave. The other waveforms have strange
artefacts, which can be nice.