John held five year old Rosie on his knee as the looked at his and Mary's wedding album. It was something they did when the little girl asked about her mum. They would take the album down and look at the photographs together. Sherlock would make a point of walking by and making 'deductions' about the guests in the photos to make Rosie giggle. Enough time had passed that it was a happy sort of thing, not painful in the least.
"What's this, Dad?" Rosie asked, pulling out an envelope from a pocket in the back of the album.
John smiled and took it from her. "Inside this envelope is a beautiful song that Daddy composed for me and your Mum to dance to on our wedding day."
"Daddy, will you play it for me? Please," she added with a flutter of her eyelashes and her hands folded together. "Please, Daddy. I want to hear it too."
The doctor cleared his throat. "Sweatie, I don't think Daddy wants-"
"Of course Daddy wants to play it for his little girl. Let me get my violin." He went and picked it up along with his bow and started tuning it. When Rosie took the envelope from her Dad to hand to Sherlock, he shook his head and tapped his temple with his bow. "I have it all up here. I keep everything about you, your Dad and your Mum up here." Setting bow to string, the detective started playing. It didn't seem as melancholy as he had expected, considering the many memories that were being stirred up. It had to be because of Rosie's look of delight.
The little girl pulled on her Dad's hand. "Come. On. Dad. You have to dance with me, like you danced with Mummy."
"Okay, sweet pea," John agreed smiling. He set the wedding album and the envelope aside and stood. He gave Rosie a little bow. "Might I have the honour of this dance?"
The little girl giggled and grabbed his hands, then they started waltzing around the room. Sherlock watched on, smiling as he played.