Ye Gods, nobody has it yet! This goes back far older than the 18th Century: according to the Brehon Law text in the Uraicecht Becc, there were a number of grades of Bard-Poet, who were regarded as equal to the political system because they carried both the heritage, both in history and law. In particular, the historic function had a certain amount of support for the political system in it, in that the bard would (if properly respected) perform in support of the local bigwig because...(and here the history of how he got there would be run off).
This form of praise continued until at least the 15th Century, possibly 16th, although by that time harpers were also suffciently often Catholic couriers as to have induced Elizabeth I to make the profession a capital offence - does anybody know if that was ever reversed? The last I know a goodly number of years ago it was still on the books.

A Planxty is a tune composed in honour of a local bigwig. Some of the examples in ITMA include lyrics with somewhat cursory history, so the practice descends from there.