From the mouth of a strict teacher comes valuable instruction.

When you cough, it's best to cover your mouth.

I bet they'll take the river rather than the forest.

When one has no useful thoughts, the ability to close one's mouth is important.

(Direct address can happen interstitially in a sentence without affecting the sentence or being a part of it in any way. Of course, this would be more common in songs or poetry than in everyday speech.)