Eyes closed, wary of stray rivulets of shampoo, John rinsed his hair and then just stood for a minute in the spray of warm water, letting it run over his neck and shoulders to relieve the tension that sometimes spread from the bullet wound in his left shoulder. He chuckled softly; maybe he would one day in his old age be able to feel the change in the weather in the shoulder, like nan used to in her knee.
Already in a good mood, John started humming along to the sound of the violin drifting in from the living room while he washed, then almost reluctantly turned off the shower, stepped out and started towelling himself dry.

By now, he knew the piece Sherlock was playing, though he couldn't remember who had composed it. It was a lively tune, dancing up and down the scales, reminding him of the songs of blackbirds in spring. John's clarinet classes at school had given him an appreciation of classical music but sadly not nearly enough knowledge.
He knew Sherlock would be deep in concentration to the exclusion of almost everything else, committing the piece to memory. Even so, John walked as quietly as he could from the bathroom to the kitchen, towel over bathrobe-clad shoulder, to make another cup of tea. He looked across the flat at Sherlock, who was standing in his customary violin-playing space, close to the sofa but with his back to the room, music stand in front of the window, blue silk dressing gown flowing from his shoulders, swaying gently in time to the music. He made no sign of having heard John. Tea for one it was then, and perhaps a quiet look at the Sunday Times crossword puzzle without Sherlock's constant interruptions.

He barely had time to get comfortable in his chair by the fireplace, tea on the side table, Times in hand, when Sherlock finished the piece with a flourish and without looking around said, "16 across is Camembert, in case you were wondering." John looked at him, eyebrows raised, but Sherlock put bow to strings again and launched into music, working his way along a chord progression using double stops before flowing into a sweet and stately melody.

"Camembert", was John's annoyed thought. Sherlock knew damn well how much John hated the genius playing co-pilot to his crossword solving. It wasn't that John was particularly good or fast at crosswords, but that wasn't the point – the point was to unwind the brain, think of things other than his job in the clinic or the cases with Sherlock, and of course for the glow of accomplishment when he finally worked out one of the cryptic clues. He didn't want help, and he didn't need help. It would be like trying to help Sherlock play the violin.

A wicked idea suddenly crossed John's mind. He might not be able to help Sherlock play, but maybe he could enhance it.

A good soldier will not rush into a situation, a good doctor will prepare before an operation, and John was both. He spent the next few minutes planning his move while watching the man who was not just his flatmate any more, as he reminded himself happily, just as he had done every day for the past few months. He watched, and he thought.

Anything in the front above the waistline was out. John did not want to impede Sherlock's playing, and besides, he did not fancy getting his eye poked out by an enthusiastic bow. Legs, yes, that beautiful backside, definitely, and probably the spine going up to just below the shoulder blades. John quickly checked the state of Sherlock's dress. He was wearing pyjama bottoms, so it was a safe bet that he'd be wearing a t-shirt underneath that dressing gown. Of course Sherlock hadn't bothered to get dressed after taking a shower – it was Sunday and there was no case, so he saw no reason. Good.

Recce completed, it was time to determine a course of action. A direct attack upon Mount Cock was out of the question; this situation demanded a lot more delicacy and deviousness. John quickly went through a few scenarios in his mind, then chose the one to which a certain part of his anatomy twitched in agreement. Still, he hesitated a little, taking the time to consider if this was really going to work or whether it should remain in the realms of stimulating fantasy. Then he noticed that he had been ogling Sherlock's bum for some time now, that silk dressing-gown sliding enticingly over it, and he made his decision.

John pulled his feet out of his slippers, got up carefully and sneaked over to Sherlock, bare feet making no sound on the carpet. He stopped just short of actually touching him, knowing that Sherlock would feel his shower-warmed body and smell the shower gel, but as he was concentrating on playing, he might not draw conclusions immediately. After a few breaths, John put his hands forward and placed them, feather-light, on Sherlock's backside. To John's surprise, Sherlock did not react and kept on playing.

Right. John recognised a challenge when he saw one.

He leaned forward slightly and carefully put his forehead on Sherlock's spine just below the shoulder blades. He almost pulled back in surprise. He had not imagined that he could feel the vibrations of the violin through Sherlock's body. Once he thought about it, it was logical, which did not make the feeling any less amazing.
He turned his head slightly, putting an ear against Sherlock's back, and smiled when he was able to hear the music through Sherlock, together with his breathing and heartbeat. It was mesmerising, and for a few moments John forgot his original plan. His hands however remembered and started stroking the warm silk over Sherlock's bum, while Sherlock played on, apparently unperturbed.

John turned his head again and started to breathe soft and warm against Sherlock's spine through silk and cotton, slowly making his way downward from one vertebra to the next, until he was crouching behind Sherlock, lingering at the top of the cleft between his buttocks, while his hands slowly moved forward, stroking Sherlock's hips, his sides, his thighs. And still Sherlock was playing as if nothing untoward was happening.

Letting his hands rest on Sherlock's hips, John focussed on what was directly in front of him, placing open-mouthed, breathy kisses on that shapely apple, occasionally nipping on it through the fabric, not hesitating to use a little teeth now and then. He loved the feeling of silk against his lips, but even more he loved knowing what lay underneath, and he gave it the attention it deserved.

John couldn't help but grin when he felt a slight tremble go through Sherlock that had nothing to do with music. But he didn't stop playing, and that was all right with John.

Now, however, the one complicated manoeuvre in John's plan was looming. Sherlock was still facing the window, and John needed more room (and, admittedly, fewer potential voyeurs) for what he was going to do. Also, he was not unreasonable. Receiving oral sex while standing up was tough enough without playing the violin at the same time, and there was a limit to how much John wanted to torture Sherlock.
He levered himself up again and, hands still on Sherlock's hips, guided the man towards the desk which was thankfully cleared of breakfast and work debris. Sherlock did not resist, until he half-leaned, half-perched on the desk, and John was kneeling in front of him, untying his dressing-gown and carefully tugging his pyjama bottoms down to below the pelvis. Only then did Sherlock hesitate, bow hovering above the strings. He glanced down past the violin, and John met his eyes.

"Concentrate, Sherlock", he said softly. "Play. If you stop, I stop."

Sherlock nodded, a slight smile on his lips. He understood rules, liked them even, when they came from John. He collected himself and started to play again. John knew the piece well enough to realise Sherlock had taken it from the top, and he grinned. A little extra time of music wouldn't hurt.

Sherlock's now exposed cock was definitely getting interested, but was still soft enough for John to take all of it into his mouth, an opportunity he did not want to waste. He lapped at it once, twice, then drew it in. It lay heavy and warm in his mouth, and he rolled his tongue around it and sucked on it gently as if it was the most wonderful sweet imaginable, a sweet that grew the more you sucked. John could feel Sherlock's cock becoming warmer and fuller until he was forced to release it, instead kissing and licking down the underside, burying his face between Sherlock's legs and breathing in the clean, warm, enticing Sherlock scent. And all the while, he was very much aware of Sherlock playing his violin.

John listened. This was the part he had been looking forward to. He started to take his cues from the music, picking up the rhythm and making it his own, following the melody up and down the shaft, teasing and licking, letting every trill become a flick of his tongue, reaching up with one hand to cup Sherlock's balls, gentling them in time to the deepest notes.

The violin became more insistent, and so did John, until the rhythm slowed and the music went soft, piano, pianissimo. John followed, his movements becoming smaller and smaller, and he glanced at what he could see of Sherlock's face beyond the violin and bow.
Sherlock's eyes were closed, his face concentrated and calm, but the rosy glow on his cheeks and his open-mouthed breathing belied that calm. Again, John followed Sherlock's lead, holding back as long as the music did, but not stopping.

He noticed a subtle shift as Sherlock realised that he could direct John through his playing, and that John would allow him to do so. John closed his eyes and swallowed. This was getting even hotter than he had imagined, and he struggled not to let his own arousal take over. He could attend to that later; now it was Sherlock's turn. And Sherlock did not stop playing.

He listened to Sherlock, letting him guide his actions through music. When the melody stayed in the higher register, John devoted his attention to the head, letting his tongue run around it and poking the tip of his tongue into the sensitive slit. Arpeggios turned into full-mouthed slides down his cock. He was happy when Sherlock found the notes that allowed him to massage the frenulum. When Sherlock played louder, John would suck hard, or nibble on the shaft; softer passages resulted in kisses and licks along the length of his dick, stroking it lightly with one hand. Lower notes still made John fondle Sherlock's balls, adding an occasional outstretched finger to stroke against the perineum. Occasionally, John would hum along to the music while his mouth was wrapped around Sherlock's cock, making Sherlock shiver under his hands.

Sherlock concentrated on playing and conducting John. John concentrated on Sherlock, on his music, both of them moving together as if they were dancing, no-one quite sure who was leading and who was following. They fell together, knowing the other would be there to catch them, the flow of music and movement and intimate touch piecing them together like a puzzle, effortless, almost timeless. John smelled the arousal on Sherlock, tasted the pre-cum leaking from his lover, and he felt himself responding, warmth spreading through him. He was convinced he could keep going like this forever, following Sherlock's lead and giving back to him as much as he could, and Sherlock's violin sung to him in agreement.

Soon, however, the music was nearing a conclusion, having come back to the original theme after many variations, and becoming more and more insistent. It was obvious to John that by now Sherlock was fighting to keep his playing under control, and he had to admire the man's force of will once again. A few driven, forceful long notes later, the music came to an end. John could feel Sherlock vibrate with the effort of holding himself together, and he looked up, taking in the heavy rhythm of Sherlock's breathing, his flushed face and neck, sweat-matted hair and fluttering eyelashes. He looked wanton and lascivious and utterly, utterly beautiful.

Sherlock opened his mouth, but no sound came out. He licked his lips, tried again. "John..." It sounded more like a low groan than a name. John hummed a question against taut skin and a high, pleading whine escaped Sherlock's lips.

"John", he managed again, his voice deep and gravelly, "... violin... don't let me..."

John looked at where Sherlock's long fingers were curled around the violin's neck, gripping it so tightly that they were almost white. He released Sherlock, reached up and gently uncurled those fingers, plucked the violin from his grasp and carefully placed it into the case next to the music stand. He did the same to the bow and turned back to Sherlock, who immediately clamped his hands on John's shoulders, drawing him close. John was only too happy to oblige. He was done teasing.

He knew Sherlock wouldn't last much longer. After only a few fast, sure strokes of his hand, mouth around the head and sucking in time, tongue licking, pressing, running around it, he could feel Sherlock's hands clench, his body growing rigid with tension, and he came with a long, shuttering cry. John felt the taste of Sherlock hit the back of his throat and he swallowed, sucking and licking and stroking Sherlock through his orgasm, until he heard him groan and felt his knees go weak.

John guided Sherlock down to the floor and wrapped his arms around him, steadying him through the aftermath, gently kissing his temple and stroking his hair. He was tremendously aroused himself, but paid that no mind. He would deal with it later, and seeing Sherlock like this was worth delayed gratification.

For a while, Sherlock just lay pressed against John, eyes closed, slight tremors running through his body like aftershocks. He eventually relaxed with a deep sigh, opened his eyes and looked at John, and John was surprised to see amazement, almost awe in his expression.

"John", whispered Sherlock, "you had clarinet classes..." He paused. John nodded encouragingly. "You told me, but I didn't realise. You have quite the musical talent."

John chuckled. "Don't bet on it. Mrs Thompson despaired of my abilities. But I am glad I was able to play that particular instrument well." He glanced down Sherlock's body, making it clear which instrument he was referring to.

Sherlock raised his eyebrows and sighed his put-upon sigh.

"What?" John asked.

"You have quite probably ruined Bach for me, you know. I'll never again be able to play that Chaconne without thinking of … this."

A wicked grin played on John's face. "Serves you right for the Camembert", he said and kissed Sherlock before he could say anything else.

oOo oOo oOo

Notes:

The pieces Sherlock plays are the Giga and Chaconne from the Partita No2 in D minor for solo violin by J.S. Bach, though I imagine Sherlock might have varied the Chaconne a little. The Partita is an amazing piece, and if Sherlock can play it, well, he's pretty darn good. I know; I've tried, and even with decades of violin playing under my belt, I can't do it justice.

For the Giga (which Sherlock plays while John is in the shower), go to youtube:
.com/watch?v=uC8qdA6uQUg

For the Chaconne (the fellatio-piece), listen to this:
.com/watch?v=5bVRTtcWmXI (part 1)
.com/watch?v=2lPZWJu1QPI (part 2. The beginning of this corresponds to the time when Sherlock begins to realise he can guide John through the music.)

Col legno is an instruction to strike the string with the stick of the bow, rather than by drawing the hair of the bow across the strings. The literal translation is "with wood". It seemed appropriate.

Thanks go to Atlin Merrick for listening to me when this idea first popped into my head, and for waving the beta-wand above the finished story.