The tune for “As with gladness men of old” has a complex history. It began as a keyboard tune by the Stuttgart organist Conrad (or Konrad) Kocher, born in 1786.
That tune (“Treuer Heiland, wir sind da” – “Faithful Saviour, we are here”) was adapted by W H Monk and W C Dix
(omitting a phrase from the original for the sake of balance) for the famous
Epiphany hymn and Christmas Carol “As with gladness men of old” and also the hymn “For the beauty of the Earth”.
It later found its way into Carols for Choir Book I in the well-known arrangement by David Willcocks.
This instrumental duo, however, provides variations upon the melody from the outset,
giving the main tune to each instrument in turn, and ends up with a waltz-time version.