If you venture into the left library on the Tower of Terror (also known as echo by the Cast Members), there's two bits of Twilight Zone lore hidden on top of each other. In the bookcase you'll see a trumpet on top of sheet music.
The trumpet is a reference to the Twilight Zone episode “A Passage for Trumpets”, which aired originally on May 20, 1960. In the episode, a man named Joey Crown decides to commit suicide and throws himself in front of a truck. After he is hit, he wakes up but realizes no one can see or hear him. Joey walks around town and is lead to a room by the sound of a trumpet. Joey meets a man in a tuxedo, who can see and hear him, and knows his name. The mystery man tells Joey that he must choose between life and death and Joey chooses life after seeing the beauty in life once more. As the man departs, Joey asks his name. The man replies, “Gabriel.”
The trumpet we see is a reference to the trumpet sound from the episode.
Underneath the trumpet is another hidden reference, but this reference has nothing to do with the Twilight Zone. Rather, the sheet music is actually a hidden Mickey. No, it's not a hiding that familiar three circle design. The name of the song is "What! No mickey mouse? What kind of party is this?", a 1932 song by Irving Caesar.