I'm interested to know whether or not the songs played in modern remembrance day ceremonies were ever played on the fields of battle to honour those who were about to give their lives.
The Last Post is a bugle call originally played to indicate the last picquet for the night is being posted (placed in position). There are also bugle calls called the First Post and Second Post. It would not be appropriate as an inspiration on the field of battle.
Private Bill Mullins, a Scottish bagpiper with 1SSB, was ordered by his Brigade Commander, Lord Lovat, also Scottish, to play the pipes, under fire, during the Brigade's landing at Sword Beach, during the D-Day invasion in WW2.
He is recorded as playing "Road to the Isles" and "Highland Laddie". "Highland Laddie " is the ceremonial quick march for the Scots Guards so it is certainly played in modern rememberance day ceremonies when the Scots Guards are taking part.
Source: Obituary, NY Times 19Aug2010 http://www.nytimes.com/2010/08/20/world/europe/20millin.html?_r=0