Back in 1986, Allen Toussaint told All Things Considered that he could write a song from the scraps of a joke, or from snippets of conversations. If the occasion called for it, he could even fashion writer's block into verse.
"Well, how do you write a song?" he offered, playfully. "Do you make it short? Do you make it long? Is there any right? Is there any wrong? Just how do you write a song?"