"Musicians" is tempting alright! However: "Milesian" gives a reasonable internal rhyme with "treason" and fits better with the whole mock-heroic tone of the song, IMHO.The song also refers to the "ninety eight" i.e. the 1798 rebellion in Ireland - by which time any ban on musicians was more honoured in the breeches (sic) than the observance!

O'Lochlainn's "More Irish Street Ballads", from which all modern versions probaaably derive,quotes a ballad sheet (no details) as source and refers to a "long rambling story and some verses" in O'Neills "Irish Minstrels". Bruce?

I must confess I had long suspected this song was, like "Monto", a modern piss-take!

Regards