Rosie sat enchanted by the music Sherlock drew forth from his violin. His nightly concerts had become part of her nightly bedtime routine. At the beginning of Sherlock's nightly concerts, Rosie clapped along with John at the end of each piece, but as the concerts progressed, she inevitably calmed and leaned her head against John's chest, her thumb going to her mouth.
Sherlock loved to play Rosie to sleep. He chose ever more sedate pieces and smiled softly each time she yawned. Invariably, his and John's eyes would meet and they took joy in the shared special moment.
Unfortunately, Sherlock chose that night to play a lovely arrangement of Saint Saens "Aquarium". Rosie's eyes shot open and she looked at his violin with the utmost contempt that a baby her age could muster, then she opened her mouth and began to wail. John and Sherlock exchanged surprised and alarmed glances. Immediately, Sherlock changed to something by Bach and Rosie settled down.
Inexplicably, from then on "Aquarium" always received the same reaction. If they heard it out in public, Rosie immediately started fussing. They never knew why. Even Sherlock couldn't deduce a reason for it.
From then on, it was stricken from their nightly concerts and Rosie drifted off to music of which she highly approved and that was all that mattered.