The product is a vintage 1936 sheet music for the song "Knock Knock Who's There?" featuring Carl Ravazza. Published by Leo Fiest Inc. in the United States, this sheet music is specifically designed for piano players at an intermediate experience level. The genre of the song is musicals, making it a unique and nostalgic addition to any collection of vintage and antique sheet music. Perfect for musicians or collectors looking for a piece of musical history to play or display.