Since the beginning of their relationship, Spock had been continually surprised by Jim. He would spend weeks studying the young captain, watching his every movement and recording his interactions with the rest of the crew. He even catalogued his behavior when they were alone in their quarters. He'd file all of this data away, analyzing it when he had a spare moment, until he was sure he had Jim Kirk figured out.
And then, in true Kirk fashion, Jim would do something completely out of the norm, and Spock would have to take new samples, collect new data, and reanalyze how he viewed his t'hy'la.
Tonight was one of those nights. He had strode into their quarters unannounced, wishing to surprise Jim. He'd gotten off-shift early, and was going to take Jim out to the observation deck to star gaze, one of Jim's favorite pastimes.
However, he froze when he stepped into their quarters. Soft music was coming from the bedroom, music unlike anything Spock had ever heard on Vulcan. It was a classical Terran song, that much he could identify. It was a soft song, one full of emotion that tugged at something in his heart.
Taking a few more cautious steps into their quarters, Spock followed the noise, standing silently in the doorway to their bedroom. A small smile tugged at his lips as he studied the source of the music.
Jim was sitting in the chair facing the mirror over their dresser, eyes closed as he played the violin, his face serene in a way Spock had never before seen.
He stayed where he was, arms crossed over his chest, content to watch and listen. The notes rose and fell in a slow rhythm, filling the room with their sound. The speed picked up towards the end of the song, Jim's hand dragging the bow across the strings quickly, fingers moving rapidly over the strings on the neck. His brow furrowed in concentration as he drew the last few notes out of the instrument, relaxing only when he lowered the bow and removed the violin from his shoulder. Opening his eyes, he grinned sheepishly when he spotted Spock in the mirror.
"I was not aware that you knew how to play such an instrument," Spock said, uncrossing his arms and stepping towards his mate.
"Band was the only thing I liked in high school. But I dropped out because…yeah. I'm mostly self-taught."
"It is impossible to tell."
"I haven't played in years."
Spock offered him a small smile and rested his hand on Jim's shoulder.
"You will have to rectify that statement, t'hy'la. It would be most pleasing to hear you play again."
"Mmm. I'll give you a private concert sometime." Jim smiled, reaching up to cover the hand on his shoulder with his own. He gave it a gentle squeeze, then released it in favor of placing the violin and bow on the dresser. Rising from his seat, he took Spock's hand again and brought it to his mouth. He pressed a soft kiss to the wrist, hiding a smirk against the flesh beneath his lips.
Spock felt a shiver go through his body at the small gesture. He allowed Jim to lead him to the bed, stopping long enough to pull him into a kiss before murmuring against his lips, "For now, I would like to hear a different kind of music."
The grin that overtook Jim's face left Spock breathless as they fell into the bed.