Halliday & Matthiessen (2014: 397-8):
Just as with the nominal group, therefore, there is no call to give a separate analysis corresponding to each of the three semantic components experiential, interpersonal, textual. The textual meaning is embodied in the ordering of the elements. The interpersonal meaning resides in the deictic features associated with finiteness — primary tense or modality — together with any attitudinal colouring that may be present in the lexical verb. And further systematic distinctions of both kinds may be realised by intonation and rhythm: contrast the neutral he hasn’t been working
// ^ he /hasn’t been /working //with a variant such as he has not BEEN working// ^ he has /not /been /working //which has ‘marked negative (polarity)’ and ‘contrastive past (tense)’, as in Figure 6-14.