Yes, clines would be used within and between levels. This may be getting
esoteric, but the notion comes from Halliday's original formulation of
his theory as scale and category grammar - with scales referring to
clines of rank (i.e. constituency - big to small to smaller units),
delicacy (general to less general to more specific categories) and
exponence (later realisation and instantiation - the langue to parole
relations we've been discussing, and also realisation between levels of
the system - e.g. discourse smenatic to lexicogrammar to phonology).
Jim Martin