This is my transcription from the recording at YouTube. Thanks to Allan Conn, above, for the suggestion and the link. It is also on Spotify:

CALLING DOON THE LINE (THE PIPER'S CALL)
Words and music by Alan G. Brydon
As recorded by Scocha on "Gie'd Sum Wellie" (2008)

1. Boys stood on the platform, 1917,
Waitin' for a train to Salisbury Plain, but only in their dreams.
A lad to his mother said in a fret: "We'll be home by Christmas day,"
And the piper played "Scotland the Brave" as he waved the boys away.

CHORUS: Callin' doon the line, callin' doon the line,
And they rallied roond to the piper's tune; it was callin' doon the line.

2. The sergeant major pushed them hard; they were trained in only days,
But to bear the brunt o' the western front would soon be on their way.
So off they marched, rifles shoulder high, and all at once they sang:
"For we're no awa tae bide awa" tae the pipers in the band.

3. The thunder echoed through the trench as the shells aboon(?) them rained,
And the gen'rals spent a thousand men for ev'ry inch they gained,
And the brave young men faced their battle dawn so proud to do their job,
And the piper stood in the line of fire and played them ower the top.

4. When No Man's Land fell silent, and they counted all the dead,
The vict'ry claimed would disguise the shame, and nothin' more was said,
And the fallen brave on a foreign field they gave their very best,
And the piper played a sad lament as they laid the boys to rest.