The term 'Merry-Go-Round Tune' is often used to refer to a lilting, cheerful melody that is typically associated with carousels and other amusement park rides. The term 'LILT' is a 4 letter word that is used to describe a light, buoyant, or swinging rhythm. Therefore, the crossword solution for the term 'Merry-Go-Round Tune' is 'LILT, ' which is a musical term used to describe a cheerful, swinging melody.