They sang that at the burial. I recently saw another movie (possibly another western, not sure) where this was sung. I think they sang it for a long time, like the scene/song went on forever. What movie am I thinking of? I can't seem to recall.
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I did sixty in five minutes once...
Check out this link to Wikipedia. Scroll down to the "In Popular Culture" section. There you will find several movies where the song was used. Maybe something will jog your memory.
https://en.wikipedia.org/wiki/Shall_We_Gather_at_the_River%3F#In_other_films
I am going to go with "Some other John Ford film." He used that song about as often as he used Monument Valley.
Datta, dayadhvam, damyata.
Is it the bank robbery scene from The Wild Bunch?
The temperance league people are parading down the street and they keep singing the song for a good 5 minutes.
https://www.youtube.com/watch?v=-i9KBsOfUPI
In "Jeremiah Johnson" Crazy Woman and Jeremiah sing it when they bury her children after the massacre. From the Goofs section: "After burying her murdered family, Crazy Woman begins singing "Shall We Gather at the River" and Jeremiah joins in. This song was written by Robert Lowry in 1864 and first published in 1865, long after the time of the mountain men."
So it was written just a few years before the time set of The Searchers.
I seem to recall it being sung at the burial of Katie Elder in "The Sons of Katie Elder" and "The Three Godfather's" all films with John Wayne in.
Let's pray the human race never escapes Earth to spread its iniquity elsewhere. C.S Lewis