This piece of music by Joseph Maurice Ravel [1875-1937] is from 1909. It was written as part of a homage to Joseph Haydn [1731-1809] who had died 100 years before.
Haydn's name occurs in the piece in different ways written out in the sheet music along with the notes. In one particular instance one has to turn the score upside down to recognize that it is indeed Haydn's name that is played according to the following rules: The letter H has become an A. H is an alternative way of naming the tone A. The letters Y and N have become D and G found by starting the alphabet on the tone A and see what Y and N coincide with tone-wise.
Pictures of settings concerning the sound of the music in the video: