Answer:
He hears Grete playing the violin in the living room.
Step-by-step explanation:
Gregor Samsa, the main character in Kafka´s Metamorphosis wakes up one day to find himself turned into some sort of bug for no apparent reason. As the story develops, Gregor spends his time adapting to his new corporeal condition while also experiencing changes to his consciousness. Towards the end of the story, he hears his sister playing the violin which makes his wish to leave his room for the first time to see and hear her sister better. This terrifies those who see him and set the scene for the final heartbreaking passages in the novella.