What is the fine-grained topic of the following text: He made his first pub­lic appear­ance in a stu­dent recital there in Decem­ber 1906, and made his for­mal pub­lic debut at the age of seven in the nearby city of Kovno (now known as Kau­nas, Lithua­nia). Only return the topic.
Public debut of a young musician