Once the initial axis-plot has been achieved it is often desirable to add a second level of complexity. Schillinger observed that melodies do not move in straight lines and so he devised a method to superimpose other forms of motion on the secondary axis directions. This is like superimosing a wiggly line on a straicht line, a form of ornamentation. In this way melodies become more flexible and complex.
Axis-sub-plot works in the following way.An axis has a displacement from the primary axis. Eg. it rises away fro the axis by an octave. (0 12). Now a further set of axis are superimposed on it. These also have displacements and directions away from their axis-axes upon axes. The directions a b c d are identical to those described in the function axis-plot.
(axis-sub-plot 0 '(a b a b) '(4 4 7 7) '(0 12))
=> (0 4 0 7 0 12)
In the above (a b a b) = directions of the sub-axes, (4 4 7 7) = the displacements of the sub-axes, (0 12) = the displacement of the main axis to which the sub-axes are attatched.
