Which song to use first depends on the amount of enemies you have at the given time. If the number is small, like 1-4 then you start with The Wanderer's Minuet, if its 4+ then start with Mages Ballad. And use Army's Paean as a filler. This helps you optimize the procs you'll get for each song. As for Troubadour, Ballad is always a safe bet, but if you know the damage the boss does using the proper version when they do a big attack is more beneficial.