The Lyrics from the play.
(As best I can make out bring a Yank)

Well whence I twas a weaver my name is Willie Broon.
And whence I was a weaver I dwelt in Maxwelltoon.
Now I am a sojor gan ta Perth and gawn awa.
For ta join that highland regiment The Gallant Forty Twa.

Oh the very first day on parade was we a lot of young recruits
and the Sgt he got on ta me but im lookin at my boots.
He tapped me on Tha shoulder and said mateie come awa.
Fer y'er sure ta make a hell ya mess for tha Gallant Forty Twa .

Ye can talk about your First Royals Your Sussex Fusseliers.
Your Aberdeen militia and ya dandy volunteers.

Your see...something or other kilts can't get it. Then something about garters ...but it ends .

Give to me the tartan of the Gallant Forty Twa ..Hope this helps. If anyone knows the last verse...I'd love to know it.