I think this song is called St Columba and the Mason. It was written by Matt McGinn, and possibly Billy Connolly. It's on one of Matt's LPs, but I can't remember the name.

Tubal Cain was a Mason
A square dealing man.
He was aye on the level
With a shake o' his han'.

Wi' his feet at right angles
He was sure to go far
Nonchalantly gein' signals
As he stood at the bar

Tell me who is your granny
He sigalled tae me
As he rolled up his troosers
Tae expose his left knee

He was fond of the folk songs
He preferred them tae jazz
And his favourite folk singer
Was called Joan Boaz

But it cost him a fortune
For these secret delights
So he told me last Tuesday
He's joining the Knights
Of Saint Columba.