Just a little moment in time, inspired mostly by my furious love for this particular piece of music by Gustav Holst, known as many different things including the quiet interlude from Jupiter, Thaxted, I Vow To Thee My Country, and Oh Merciful Redeemer as well as many other hymns. I am not a religious person so I am not terribly fond of most of the versions with lyrics, but the music is incredibly beautiful and always makes me very emotional. You can read more about it on Wikipedia by searching for "Thaxted (Tune)".
The version of the piece I imagine Sherlock to be playing sounds very much like this incredible rendition, slightly slower and sadder than the way it's usually played, and adapted to focus nearly entirely on the violin. - youtube (dot) com/watch?v=hKq8xsUr5dA
The flat at 221-B Baker Street is quiet. John is settled solidly into the comfortable, overstuffed armchair with the Union Jack cushion supporting his lower back, and Sherlock is folded with his feet tucked up under him in the wide leather Corbusier armchair that's always looked slightly too glamourous and out of place in the flat, much like the man sitting in it.
It's a good quiet. The soothing, comfortable quiet after a case – not the anxious, unsettling quiet before all hell breaks loose. The sun is starting to set and it's suffusing the flat with a warm golden glow. John pauses to turn the page on the book he's mindlessly half-reading and sees Sherlock lean over the side of his chair and gingerly lift his violin case up into his lap. He unfolds himself from his ridiculous contortion and sits up relatively straight, opening the case and pulling the violin out. John marks the page in the book that he wasn't really paying attention to in the first place and lets it fall to the floor, his gaze locked on Sherlock. Generally, the noises the taller man produces with his violin are aggressive and offensive, but there's an understanding in the air right now. His movements are calmer, more respectful of the incredible instrument than usual, and they both know that whatever sounds he's about to produce will only serve to compliment the quiet that has settled on the flat, not to destroy it.
Sherlock's long, dextrous fingers turn the pegs just so, with a delicate efficiency of movement. He places the violin on the arm of the chair and pulls out his bow, sliding the rosin along it with the same sensual attention he paid to the violin itself. Slowly, he raises the violin to rest at his chin and holds the bow loosely between his fingers. His eyes lock with John's, inquisitive and just a little challenging. Almost as if he's asking permission to break the perfect silence that's surrounding them. John's eyes meet his gaze and one corner of his mouth turns up in a slight, encouraging smile. He knows that if either of them actually verbalizes anything, it will ruin the moment.
Translucent lids fall down over pearly grey eyes and Sherlock pulls in a deep, meditative breath. John shifts his weight in the chair, transfixed by this side of Sherlock he's so rarely allowed to see. The bow hovers over the strings of the violin for a moment before dipping down and producing one low, tremulous note. Finally giving in, Sherlock lets the notes flow from his glorious fingers through the delicate instrument and into the perfect air, weaving itself in and out of the silence rather than interrupting it. The tune he plays is slow and sweet and a little bit sad, but filled with an undercurrent of immense power. It's incredibly familiar to John, and yet it's like nothing he's ever heard before. For a few minutes, the world ceases to be anything other than music and breathing and dust motes in sunlight.
Drawing out the last note just a fraction of a beat longer than necessary, Sherlock lets the violin drop gently back into his lap and looks up at John, who wipes his eyes quickly, nods at Sherlock, and goes back to his book.