What is an elf's favorite kind of music?

This joke plays on the double meaning of the word “wrap.” In one sense, “wrap” refers to a genre of music, specifically a misspelling of “rap,” a popular style characterized by rhythmic speech and beats. On the other hand, “wrap” is also a verb associated with covering or enclosing something in material, such as gift wrapping. Elves, in popular culture, especially around Christmas, are often depicted as Santa Claus’s helpers who make and wrap presents. The humor emerges from the pun where “wrap” music humorously suggests a musical style that could be favored by elves due to their association with wrapping gifts.