The Pomp and Circumstance Marches are a series of five marches for orchestra composed by Edward Elgar. In the United States, the Trio section "Land of Hope and Glory" of March No. 1 is often known simply as "Pomp and Circumstance" or as "The Graduation March" and is played as the processional tune at virtually all high school and most college graduation ceremonies. It was first played at such a ceremony on 28 June 1905, at Yale University, where the Professor of Music, Samuel Sanford, had invited his friend Elgar to attend commencement and receive an honorary doctorate of music.

Source: Wikipedia