It was a regular old night in the TARDIS- Rose had gone off to bed, and the Doctor, with his "superior Time Lord biology" remained awake and tinkered with the old mechanisms, or perhaps roamed around the TARDIS's endless rooms (which the Doctor long since knew all by heart) doing who knows what. But there was a minute difference in that particular night, however.
Rose awoke from a dreamless sleep, startled at a certain noise drifting distantly through the expansive halls. It was a normal occurrence for random noises to come up now and then, it wasn't a usual occurrence to hear a shrill and piercing melody, so high and mournful that it made the hairs on the back of Rose's neck stand on end, even under her overabundance of velvety fuchsia and lavender blankets. Obviously startled, Rose sat up and slipped on her grayish-blue bathrobe hanging on her bedpost and the slippers by her bed. The disturbing noise rose and fell with volume, growing soft and tender and some points and then rising with flowing grace into a cold, high pitch, filled with numerous, almost inexplicable emotions. It was stunning, almost disturbing, haunting even, but beautiful nonetheless. Curious, Rose followed the trace of the noise, treading softly through the dim, peaceful halls.
With every step, the noise grew clearer and sharper with tone, and it became less like random notes scattered here and there, but a thought- out composition of music, clearly being played by a violin. There was only one other person on the ship besides Rose, but it couldn't possibly be him. He was devoid of any affection as long as she had known him, unreachable by human warmth and comfort. But maybe this is how he copes with the loss that Rose had only gotten a brief glimpse of; maybe this is how he expresses his held-back tears over the loss of his people. It was only now that Rose realized how much pain the Doctor was in, is in, in fact. He had a wound that would never heal that he tried to patch up with trifle things like playing a lonesome tone on a violin, or a sleepless night wandering through the TARDIS halls, hoping to forget, or Rose herself, the simple act of companionship treating that wound like medicine.
Relying on the precision of her hearing, Rose finally found her way to the source of the delicate tune. Rose barely peeked her head into the dusty old room - which was empty with the exception of a couple of old chairs and a fireplace- just enough to see the sorrowful scene. And sorrowful, indeed it was. In the center of the bare, musty room stood the Doctor, cold and composed, striking each note intently with such vigour that even as emotionless he might seem to appear, no one could have said that sorrow not the motivator of the striking waltz. The old, wooden floor creaked beneath the Doctor's feet as he moved in a seamless series of strides as the unique sound of the violin vibrated throughout the walls of the barren room, the pitch of the frightening song spiraling downward in a horrifying but wonderful tragedy. Rose felt a single tear travel down her cheek as it continued.
Both afraid of discovery and the music become unbearable, Rose traveled noiselessly back to her bedroom, and returned to her warm blankets and pillows, as if her venture to the Doctor's room never happened.
But a few hours later, Rose returned to the scene to find that the noise had stopped, and surely enough, the Doctor had drifted to sleep, slumped in one of the chairs with violin still in hand.
So Time Lords can sleep, Rose thought. And with sympathy and affection for her daft Time Lord with the large ears and the gleaming blue eyes, lightly pressed her lips to the Doctor's forehead and left without a word.
And the Doctor, who had sensed her entry and surveillance from the moment Rose found the little abode, could not suppress the smallest of smiles as Rose left the room.