Many people already know that music for the familiar Christmas carol Hark! the Herald Angels Sing is credited to Felix Mendelssohn.
Through a series of messages on the LETPRESS mailing list, I found out just recently that the original Mendelssohn work was written to celebrate the 400th anniversary of Johannes Gutenberg’s development of a workable system of printing with moveable type.
This work was played June 24th 1840 in the marketplace in Leipzig as part of a Gutenberg festival, and consisted of four parts, the second of which became the Chritsmas carol. The music was written for four male singers and two small brass orchestras, with the footnote (courtesy of Google Translate):
The second small orchestra must be placed at a great distance from the first to make it the same as an echo replies
Parts of the score have a call-and-response structure and Mendelssohn added this note to ensure the responses would sound distant. Clearly this was designed for the open-air venue in which it was first performed!
In adapting the music in 1855 to hymn lyrics by Charles Wesley, William Hayman Cummings took the main melody from the second part, omitting the central bridge, producing the carol as we now know it.