One great inspiration is incomprehensibility.

Most of what I've looked at in this area is about the history of Edinburgh. Most of that was about the connotations of instrumental music, and when I dealt with songs they were usually broadsides long forgotten.

Pick an instrumental tune: William Marshall's reel "The Illumination 9th Feb 1781". What the heck is that about? You need to look at local newspapers to find out. The story turns out to be an explosively dramatic one, marking Edinburgh's moment in a series of events when Britain came close to all-out insurrection.

Or a broadside about a hastily adapted prison camp near Edinburgh for French captives of the Napoleonic War:

The moon o'er the waves of the North throws her glory
And brightens the snow wreaths on proud Pentland high,
Whilst cold, under arms, I view, leafless and hoary,
The dark wood that answers the sentinel's cry.

But what are my sufferings, though cold, wet and weary,
And round me the rude blasts of insult blaw shrill
To theirs who're confined in the dungeon so dreary
And wail life away in the gloom of Esk Mill...

As it happens, we can date that one, purely on internal evidence, within about three weeks. The mill was so rickety it came close to crumbling into a heap of rubble on top of the prisoners and was hastily abandoned. But it was open just long enough for an anonymous Scottish broadside writer to take up the issue of how the prisoners were being treated.