“So which is it?” Perez said. “Yes or no?”

“No,” Middleton said. “But only inadvertently. I made a couple of mistakes. I guess I wasn’t thinking too straight.”

“What mistakes?”

“Concert pitch is a fairly recent convention. Like international time zones. The idea that the A above middle C should be tuned to 440 cycles started way after both Mozart and Chopin were around. Back in the day the tunings across Europe varied a lot, and not just from country to country or time to time. Pitch could vary even within the same city. The pitch used for an English cathedral organ in the 1600s could be as much as five semitones lower than the harpsichord in the bishop’s house next door. The variations could be huge. There’s a pitch pipe from 1720 that plays the A above middle C at 380 cycles, and Bach’s organs in Germany played A at 480 cycles. The A on the pitch pipe would have been an F on the organs. We’ve got a couple of Handel’s tuning forks, too. One plays A at 422 cycles and the other at 409.”

Perez said, “So?”

“So Faust’s calculations will most likely come out meaningless.”

“Unless?”

“Unless he figures out a valid base number for A.”

“Which would be what?”

“428 would be my guess. Plausible for the period, and the clue is right there in the Mozart. The 28th piano concerto, which he never got to. The message was hidden in the cadenza. If the 28 wasn’t supposed to mean something in itself, they could have written a bogus cadenza into any of the first twenty-seven real concertos.”

“Faust will figure that out. When all else fails. He’s got the Mozart manuscript.”

“Even so,” Middleton said. He turned to Kaminski. “Your uncle would have been ashamed of me. I didn’t account for the tempering. He would have. He was a great piano tuner.”

Perez asked, “What the hell is tempering?”

Middleton said, “Music isn’t math. If you start with A at 440 cycles and move upward at intervals that the math tells you are correct, you’ll be out of tune within an octave. You have to nudge and fudge along the way. By ear. You have to do what your ear tells you is right, even if the numbers say you’re wrong. Bach understood. That’s what The Well-Tempered Klavier is all about. He had his own scheme. His original title page had a handwritten drawing on it. It was assumed for centuries that it was just decoration, a doodle really, but now people think it was a diagram about how to temper a keyboard so it sounds perfect.”

Perez took out a pen and did a rapid calculation on a napkin. “So what are you saying? If A is 440, B isn’t 495?”

“Not exactly, no.”

“So what is it?”

“493, maybe.”

“Who would know? A piano tuner?”

“A piano tuner would feel it. He wouldn’t know it.”