I do not own anything dealing with Harry Potter. This is for my own amusement.
The old Wizarding hat was sitting on a shelf, muttering to itself. Most people who came across it would find it strange, as old hats usually don't sing. In fact, new hats don't sing either. However, as he entered, Dumbledore smiled to it and greeted it calmly as though it was an old friend.
"Have you gotten much done today?" the elderly wizard asked it, sitting down in an armchair and spreading a few papers out on the desk. He glanced at a newborn phoenix next to him and reached out a hand to pet it.
"Of course I got plenty done," the hat snapped back, its brim wrinkling into a frown. As Albus Dumbledore gave the school Sorting Hat a long look, it gave in. "No, nothing."
"Well, I suppose you still have a few months left."
The Sorting Hat gave an indistinct sound but said, "Years ago, I could have whole sorting songs come in as soon as I was put up here on this shelf. I could make one up as soon as I got out there. Now it takes me three months to think of one line!"
"I suppose you've used your best lines already then."
The old hat was getting fed up with Dumbledore's simple remarks to him. It tried to think of something else to say.
"Doesn't anyone ever clean this shelf?"
Dumbledore looked over his shoulder, took out his wand, and waved it. The dust vaporated into air. Silence hung in its place.
"What about 'You may not think I'm pretty –'?" the hat asked hopefully, feeling that the line would be perfect.
"I believe you used that one back in… ah, 1992, I believe. Possibly 1991. You've never re-used a line before, have you?"
"The trick," the hat told him happily, "is to use the line again once everyone from that year is gone or has forgotten. I can re-use it every seven years."
Dumbledore turned in his chair, giving the hat an amused look. "It's only been five years, however."
"Kids these days don't remember a thing," the hat snapped back at the wizard. Sings were always ruined by Dumbledore, who could remember very far back into the past.
Dumbledore nodded, which was strangely unexpected for him to agree with such a comment as that. "I suppose you could get away with doing that early."
"These songs are harder than they seem," the hat announced as though threatening the Headmaster.
"They take a long time. I bet no other person could think of so many this quickly."
The Sorting Hat fell silent. Dumbledore read through the papers for a moment.
"Can I quit this job?"
Albus Dumbledore turned around quickly, his face carefully blank. "Quit?"
"Yes. Can I stop singing these songs? I mean, if the kids want to know what I always say, why not mention it to an older student. They can say, 'Oh? That old hat? Yeah, he just sings about them houses and sorts us.'"
"That's the point," Dumbledore pointed out. "We need someone to sort the students, not just explain the main idea of Hogwarts the history."
"Oh, so now I'm a bad history teacher now, am I?"
A blue eyes stare met eyes that were not on the hat.
"I never said that."
The hat tried to snarl to no avail.
"Fine then. Our deal is I don't sing but I'll grace the students with my gift of sorting. I mean, no human could ever do that."
"I imagine Severus would be very happy taking on the singing job, then," Dumbledore responded, marking a piece of parchment and smiling.