On 9 May 2012, on the Sysfling list, S.S. Deol wrote:
Dear AllYou may comment on the use of would in the following sentence taken from an interview of a film actor:
I was doing what the script demanded and my director would scream at me saying......
A good question! It has a simple answer, but it is one that upsets the neat patterns of system networks that we systemicists like to draw (e.g as discussed - and exemplified - in Bache, Carl, 2008. English Tense and Aspect in Halliday’s Systemic Functional Grammar: A Critical Appraisal and an Alternative. London: Equinox). …
In a systemic functional grammar, the meaning of an item such as would is captured by the selection expression of features that have been 'chosen' in the traversal of the system network. In the Cardiff version of SFG the meaning of would in the key clause of your text-sentence (my director would scream at me) is expressed by the following selection expression (where 'trp' stands for 'time reference point'):[past trp, real, long period in past, repeated].
(Here 'repeated' stands for 'repeated regularly'.) It has no connotations of 'will', 'willingness', 'intention' etc, as other uses of would have. Its nearest systemic relationship is with another meaning that lies outside the canonical model of 'time', i.e. used to, in which the meaning is, in terms of its semantic features:[past trp, real, long period in past, simple].
So we can refer to the multiply repeated event in your example by saying eitherMy director would scream at me.or, using the closely related meaning that does not restrict the meaning to repeated events, represented here by [simple]:
My director used to scream at me.
But the first is the more precise meaning, because it expresses both 'long period' and 'repetition'. In contrast, with a 'stative' process such as 'living' we can only say I used to live in London and not *I would live in London, because part of the meaning of would is that the event was repeated over a relatively long period of time. (In contrast, we CAN say I would stay with my aunt (whenever I visited London, because 'staying' lasts for a relatively short period of time.) So the 'aspectual type' of the process of the event interacts in complex ways with 'time meanings'.
The simple answer is that, in the SFL framework, this would functions interpersonally as the Modal operator of median usuality that realises the Finite element in the Mood of the clause as exchange. The relevant system networks are on pages 135 (clause) and 349 (verbal group) of Halliday & Matthiessen (2004).