A mordent is a musical ornament that involves a rapid alternation between a note and the note immediately below it in pitch. It is typically notated with a specific symbol in sheet music, indicating to the performer how to embellish the melody. Mordents can add expressiveness and flair to a piece, enhancing its emotional impact. There are two main types of mordents: the upper mordent, which starts on the main note, moves to the note below, and returns to the main note, and the lower mordent, which begins on the main note, goes to the note above, and returns. These ornaments are commonly found in the works of composers like Johann Sebastian Bach and Wolfgang Amadeus Mozart.