Unit generators are created by the audio and control generic functions, which specify audio or control rate operation, respectively. Some signals produced by unit generators vary at audio rate, such as a sine tone or the amplitude input for an amplitude-modulated signal. Others vary much more slowly, such as panning position for a slow crossfade. Your choice of construction function determines which behavior to use. Most generators support both modes of operation, although some are better suited to one or the other. Reading in a sound file from disk can only be done at audio rate, while graphical controls all operate at control rate.
The first parameter to these functions is the class of unit generator to create. The rest of the parameters depend on the class being created. Most generators have sensible default for all inputs, even audio-rate inputs, so just passing the class normally succeeds:
ss> (audio sine) #<<sspad> 410a2500>
These functions return the output port of the graph. If there are multiple outputs, a list is returned. In this case, there is only one output, as we could verify by looking at sine's help file (see Runtime Help).