Why Worship?

Ok, so I've got my cynicism back in full force, and why not? It is Sunday after all! One thing that most of the churches I've ever been to does the same every Sunday is to play at least one worship song after the sermon.

Why do they do that? Is there some theological reasoning behind it?

Is it the only way we can leave church feeling good?

It wasn't an issue for me this week, but last week the Pastor preached a really interesting sermon, something I would have liked to ponder. But noooo, the only thing I had on my mind after leaving church was the inane words to Israel Houghton's Friend of God;

I am a friend of God
I am a friend of God
I am a friend of God
He calls me friend

He calls me friend? All I could think of on the way home was - is that really Biblical? Does it say anywhere in the Bible that God wants to be our friend, or is that just some modern feel good wishy washy watered-down theology?

What was it that the Pastor spoke on? I just can't remember.