I should have mentioned that an historic era which might have caused a flurry of composition and where knowledge of Irish might not be necessary for its examination, is that of the Spanish Civil War. I am not aware if there are/were songs about it in Ireland and whether these were songs of the Irish in Spain at the time or not. That might be a fruitful avenue of research - and then again...

It certainly had a marked effect on the work of the Scottish Gaelic poet Somhairle Mac Gill-Eathain, Sorley MacLean who is worth reading even in translation. And he didn't actually go!