"This plate is needed for a music box to play."
The Music Box Plate was found in the Palace at Rockfort Island in Alfred Ashford's bedroom. When going through the Palace, Claire Redfield had to use the King Ant Object and Queen Ant Object to unlock Alfred's and Alexia's music boxes, take the Music Box Plate out of one, and put it in the other. Doing this revealed a secret passage to a hidden alcove room. Another one is found in the replica of the twins' private house in Antarctica. The same as the former applies similarly; however, gems are needed to complete the ants on top of their music boxes.