"Hark, the Herald Angels Sing" is a Christmas carol that has become a classic holiday tune. However, it's important to note that the melody commonly associated with the carol was not originally composed by Felix Mendelssohn.
The melody Mendelssohn composed is actually from his cantata "Festgesang" (Festival Song), which was written in 1840 to commemorate the 400th anniversary of the invention of the printing press by Johannes Gutenberg. The original lyrics for "Festgesang" were in German and had no connection to Christmas.
The English lyrics that we associate with "Hark, the Herald Angels Sing" were written by Charles Wesley, the brother of John Wesley, the founder of the Methodist movement. The lyrics were initially part of a hymn titled "Hymn for Christmas Day" and were later adapted to fit Mendelssohn's melody.
So, while Mendelssohn's composition played a crucial role in the creation of the carol, it wasn't originally intended for Christmas, and the lyrics were added later by Charles Wesley. The collaborative result has since become one of the most beloved and widely recognized Christmas carols.