A/N – This is a story that grew out of a piece of music sent to me by mattsloved1 and a conversation with ScopesMonkey about music. Not much more than simple fluff. Thanks to Scopes for going over this for me as well.

Warnings – Not a one that I can think of.

Disclaimer – I don't own a thing.

Cello Suite No. 1

Sherlock had his microscope turned up to the highest magnification as he examined the sample on the slide. He was engrossed watching the parasites move around. John has obtained a sample of Blastocystosis for him from one of the lab workers at the surgery. Apparently they'd had a patient being tested and it had shown up. Sherlock smiled as he remembered John handing over the tightly sealed petri dish.

"If I get sick from this I will break all of your equipment." John hadn't released his grip on the dish. "And I won't have sex with you ever again." Sherlock's frown had grown but he'd nodded his understanding and had mentally formulated ways ensure complete containment of the parasite. John had finally released the petri dish and gone to take a shower. Sherlock knew that his husband had resigned himself to sleeping alone that night.

He pulled out one slide and slipped in another – this one he'd exposed to a different complex protein combination. He was focusing the lens when heard the first sound. Sherlock recognized it immediately as a nightmare noise and frowned as he started analyzing the parasites. It was exactly three minutes later when the next noise – a groan – came down the stairs. It was the groan that John gave when he was having a nightmare about Afghanistan. Sherlock stiffened as he changed the slides out again.

He silently hoped that the noises would stop. He told himself it was because the experiment would be interrupted, but he knew that was untrue. He didn't like it when John was upset. He tried to shake the discomfort away but the muscles along his spine would not relax.

Sherlock put the first group of slides away and was in the process of opening the second when the bed shifted on the wood floor above his head. His neck ached as the muscles contracted before he managed move his head from side to side to stretch them out. John was tossing and turning in the bed, indicating that it was not a nightmare that was going to go away on its own. Sherlock put the boxes away into a safe container and, as if on cue, heard John gasp. The doctor was going to wake himself up soon.

Sherlock glanced at the stairs just as the shout was cut off almost before it began. It was the distinctive "Sh-" sound and Sherlock frowned again. It meant it was John's recurring dream of Sherlock dying in Afghanistan, usually on John's own surgical table. Sherlock didn't understand that particular dream; he'd never been to Afghanistan and had no intention of ever going. Sadly dreams – particularly John's – were rarely rational.

Sherlock picked the black instrument case up off the floor and snapped it open. He pulled the bow out and tightened it before removing the violin. Sherlock heard John's footsteps moving across the hall and into the bathroom. The detective started climbing the stairs as John turned the water on. "Chasing the ghosts away" John often said and Sherlock didn't like the imagery.

Sherlock stood in the door way and eyed his husband. The collar of John's t-shirt was damp from where he washed his face. His elbows were locked as he leaned against the counter, head hanging down. Sherlock had the urge to touch him. He stayed still though, having learned in these moments that physical contact often caused more harm than good.

"I'm sorry," John said after a moment. Sherlock nodded even though it couldn't be seen. There was no need to point out the apology was ridiculous. It was not as if John chose to disrupt Sherlock's experiments or as if he was being voluntarily miserable. John often apologized when it wasn't necessary and Sherlock had just learned to accept it.

John looked up and Sherlock watched the familiar blue eyes trail over the violin. After a moment the doctor nodded and pushed himself up. He shook his head violently and moved to close the door.

"I need to use the loo," he said and Sherlock took a step back. The detective listened for another second before making his way into their bedroom and sitting on his side of their bed, his back against the headboard. He stretched his long legs out in front of him and sat his violin on his lap, mentally settling on piece to play.

He remembered the first time he'd played specifically for John. It hadn't been long after they'd become lovers, and Sherlock had been working on the Hungarian kidnapping case. When Sherlock was a child he played the violin because his mother had insisted upon it. He'd enjoyed it enough and it often kept him occupied when he'd become bored. As he'd grown older he played to clear his thoughts. The tone, the melody, the pattern of the notes always helped him to think. His thoughts would organize and begin to coalesce as the music lifted off the strings and he'd begin to understand.

But John Watson, being life's great contradiction, had entered the living room that night while Sherlock played and done something that no one else had done before. He listened – really listened – and enjoyed. Sherlock had watched John on the couch. He'd studied the doctor's face as the music moved him. His blue eyes had closed and John's body had gently swayed to the sounds. With a swelling in his chest Sherlock realized that he was responsible for it. His playing was doing that to John, and John liked it.

For the first time in his life Sherlock loved to play simply for the music. He'd play John's favorites when he wanted to make his husband smile or more complicated pieces when he wanted to impress him. And Sherlock had realized, almost on accident, that his playing eased John's post-nightmare insomnia.

It had been after a case involving several men smuggling weapons to Afghanistan. Sherlock had been expecting the nightmares that night and had started playing to keep himself occupied while waiting for them. He'd been in the middle of a Chopin piece when John quietly came down the stairs and settled on the couch. The piece was new to Sherlock and he intended to just play through the end of the movement before turning his attention to John. When he'd finished and turned to John, the doctor had been sound asleep again. The image had created a hypothesis that had yet to be proven wrong.

John entered the bedroom and looked at Sherlock apologetically for a moment before moving to climb into bed. Sherlock watched every movement, picking up the violin when John settled on his back. He tucked it under his chin.

"Request?" Sherlock asked even though he knew John wouldn't have one. In these moments it didn't matter what he played, just that he played. John shook his head and buried his face against Sherlock's thigh. He bunched his arms between his chest and Sherlock's leg, not across them, because he knew Sherlock would get up again as soon as he fell asleep.

"Bach I think," Sherlock said bringing the bow to the strings. As the first notes of Cello Suite Number 1 eased around the room he felt John relax.

The piece mattsloved1 sent me was The Piano Guys Cello Song, it's based on Bach's Cello Suite No. 1. A truly beautiful piece.