//Sissi thinks in music and expresses her feelings through it.
Years of humming and singing songs made her to have a really nice and high singing voice.
If she is insecure about someone or uncomfortable with her sitaution she starts humming ,,Swan lake" by Tchaikovsky.
If she is excited or angered she hums ,Flight of the bumblebee'.
If she is sad she'll hum Passacaglia in C-minor by J.S. Bach.
She hums classic music only and all the versions she hum are the ones played in a higher octave than usual to fit better with her voice.
She also thinks in music.