The "Saddest Songs of the Season" essay at Songfacts led me to the James Taylor/Mark O'Connor video used for PBS' "Liberty! The American Revolution" 1997 miniseries. Just the song that Joseph Plumb Martin would have heard/sung on his way from New England to Valley Forge and back again.
Marching songs of the American Revolution
Songs Mail Carrier Cliff Clavin marches to...