[Pitchwife]

But it was no orc-chieftain or brigand that led the assault upon Crickhollow.

I only noticed this because Aiwendil mentioned the ambiguous horn-call/cock-crow that Frodo heard in Bree, but the attack on Crickhollow actually foreshadows - in miniature model, so to speak - a famous scene much later in the book.

First read this:

There was a blow, soft but heavy, and the door shuddered.
'Open, in the name of Mordor!' said a voice, thin and menacing.
At a second blow the door yielded and fell back, with timbers burst and lock broken. The black figures passed swiftly in.
At that moment, among the trees nearby, a horn rang out. It rent the night like fire on a hill-top.
Awake! Fear! Fire! Foes! Awake!
[...] The Brandybucks were blowing the Horn-call of Buckland, that had not been sounded for a hundred years, not since the white wolves came in the Fell Winter, when the Brandywine was frozen over.
Awake! Awake!
Far-away answering horns were heard. The alarm was spreading. The black figures fled from the house.

And now compare it to this (from The Siege of Gondor):

A deep boom rumbled through the City like thunder running in the clouds. But the doors of iron and posts of steel withstood the stroke.
Then the Black Captain rose in his stirrups and cried aloud in a dreadful voice, speaking in some forgotten tongue words of power and terror to rend both heart and stone.
Thrice he cried. Thrice the great ram boomed. And suddenly upon the last stroke the Gate of Gondor broke. As if stricken by some blasting spell it burst asunder: there was a flash of searing lightning, and the doors tumbled in riven fragments to the ground.
In rode the Lord of the Nazgûl. A great black shape against the fires beyond he loomed up, grown to a vast menace of despair. In rode the Lord of the Nazgûl, under the archway that no enemy ever yet had passed, and all fled before his face.[...]
And in that very moment, away behind in some courtyard of the city, a cock crowed. Shrill and clear he crowed, recking nothing of wizardry and war, welcoming only the morning that in the sky far above the shadows of death was coming with the dawn.
And as if in answer there came from far away another note. Horns, horns, horns. In dark Mindolluin's sides they dimly echoed. Great horns of the North wildly blowing. Rohan had come at last.

Wow! Looks like the Nazgûl are knee-deep in **** whenever somebody has the courage to blow a horn on them.
But seriously: To me, the correspondence, detail for detail, seems much too obvious for this to be a mere coincidence - especially as it's Merry (one of those annoying horn-blowing Brandybucks) who deals the Witch-King his penultimate blow in the chapter following the second quotation. Moreover, both scenes are echoed together when Merry blows the Horn-call of Buckland on the Horn of Rohan during the Scouring of the Shire. An awesome example of Tolkien's narrative skill creating coherence over long distances.