Charles Wesley's words were adapted by various contributors – notably George Whitefield, another of the founders of Methodism – into the version that we're so familiar with today.
Wesley's original version, written in 1739, opened with the words "Hark! how all the welkin rings / Glory to the King of Kings"; and he gave it the rather prosaic title Hymn for Christmas–Day. A version published in 1758 had several changes, including the more familiar opening "Hark the herald angels sing / Glory to the new–born King!". Further changes appeared in a version published in 1782, including the repetition of the opening couplet at the end of each verse.
Wesley envisaged his words being sung to the same tune as his Easter hymn, Christ the Lord is Risen Today – which was first published at the same time, and entitled Hymn for Easter Day. The original tune used for the latter, entitled Maccabeus, was composed by George Frideric Handel for his 1747 oratorio Joshua. It's most commonly used today for another Easter hymn: Thine Be the Glory. (The tune that we most associate today with Christ the Lord is Risen Today was composed by one Robert Williams in the famous Anglesey village of Llanfairpwllgwyngyll, and named Llanfair.)
It wasn't until 1840 that Felix Mendelssohn composed a cantata to celebrate the invention of moveable type printing by Johann Gutenberg. Hark, the Herald Angels Sing! finally took on the form that we know today in 1855, when Mendelssohn's tune was adapted by the English musician William H. Cummings to fit its lyrics.
Sir David Willcocks, director of the choir of King's College, Cambridge, added a descant and a last version harmonisation for organ. Willcock's version was published in 1961, and for many years it's been used as the recessional hymn for the annual Service of Nine Lessons and Carols at King's College Chapel (which has been broadcast by the BBC since 1928).
Wikipedia has a rather unflattering portrait of George Whitefield.
© Haydn Thompson 2021