Why does piano playing make holden feel even louiser than before?

Piano playing does not make Holden feel even lower than before. Instead, listening to his sister, Phoebe, play the piano makes him feel "sorta sad and depressed" but, at the same time, brings him immense comfort. Amidst all the chaos and isolation Holden experiences throughout The Catcher in the Rye, Phoebe's piano playing reminds him that there are aspects of life still capable of touching his emotions and humanizing him. However, it does not make him feel low.