"A screaming" - question to native speakers

[Paul Mackin]

On Wed, Jul 1, 2009 at 11:59 AM, Che Molava<chemolava at googlemail.com> wrote:
> (Paul Mackin)>> There are possibly many screamers or sources of the screaming.
> A chorus of terror: "Now everybody".
>

Everybody's screaming comes across the sky.

Somebody's screaming comes across the sky.

I had myself sort of convinced this morning that "a" supplies an agent
for "screaming" (someone or something we know not what) but now I'm
losing confidence in that idea.

I still for the life of me can't suggest to Janos what the "a"
contributes to the sentence.  Information he might need in making an
accurate translation.

O me.

P