Articles: In most contexts, [the/a] speaker and listener would not be surprised by specificity.

Good moring, everyone.

In another thread the following sentence popped up as a side topic:

1) In most contexts, speaker and listener would not be surprised by specificity.

The author used zero article before 'speaker and listener' to express a general statement. As far as I know, we can also use the definite and indefinite articles to speak generally. In this case it would be:

2) In most contexts, a speaker and (a) listener would not be surprised by specificity.
3) In most contexts, the speaker and (the) listener would not be surprised by specificity.

Could you please explain in what context would you use 1), 2) and 3)?