The feeling of overwhelming sorrow hit John without warning. At first, he didn't understand where the music was coming from, thought it was a grief-induced hallucination, brought on by not enough sleep and the shadow of his best friend. There was no reason for there to be music unless it had come from his head. He dismissed it without a second thought.
He couldn't bear to go to work that day, not so soon after Sherlock's death, not with the music playing. Mournful strings, how oddly appropriate a soundtrack to think back on Sherlock's death. But the tune kept playing over and over, as if Sherlock was a ghost, haunting him by living on as nothing but music, relentlessly agonizing John with one final hint of a future that could have been.
It played all day. It played all night. There was nothing John could do to stop the music he was certain was only in his mind. He tried to keep some semblance of sanity, a façade that it was only grief that plagued him and not the music. Sherlock's ghost was always there, just on the edge of hearing, just out of reach.
"Damn it, Sherlock," he said to the air. "Just one moment of…of peace, please, for God's sake!" But the music kept playing. The ghost was loudest by Sherlock's chair, in the chair, as if the ghost was just…sitting, waiting for something. Or maybe watching John.
Before long, John took comfort in it. He stared at the chair, trying to see the ghost that reason told him wasn't there. The music kept playing, over and over, and John had long since memorized it. Any hope of clemency was gone, so John decided to embrace the ghost of 221B. Sometimes he'd talk to it as if it were Sherlock, telling him about his day, saying how hard it was without his best friend, sometimes demanding an answer as to why he'd jumped from the roof. He'd never get anything, of course, just the music, but it made John feel a little better to try.
One afternoon, as he listened to the ghost, it fell silent. Utterly silent. The musical ghost of Sherlock Holmes had left for good, every wisp of the brilliant mind forever gone.
John began sobbing, both angry and helpless, an aria of pain rising to the deafening silence that suddenly settled over 221B. "Why did you leave me? Why? Don't you understand? This hurts, you selfish bastard! This hurts!" He flung himself at the empty and silent chair, hitting it with all his might, trying to beat his friend back to life, or force the music to continue playing, anything, any sign that something of Sherlock was still alive, or unalive, or whatever, just some sign that he was there. He saw a gleam of silver from inside the cushions, and reached for it. Sherlock's iPod had fallen down in the cracks of his chair, and the screen was dark, the battery having run down from its constant repetitions of the Adagio for Strings by Samuel Barber. John collapsed into the chair. There had been no ghost. He had no contact with Sherlock after-death. That connection was severed forever.