Declan, that's the point I would make, but I don't have the knowledge of Irish music to argue the point.

Maybe they're just playing the tunes as they learnt them not knowing any different. There is an understanding that if you hear someone play a tune a certain way, then that's the way to play it. That goes for singers as well as musicians. Right or wrong???

To get back to the 'metronome' idea. I was recording dance tunes with an Enlgish band. The tempo was all over the place. The recordings are very popular with English dancers. The musicians are long time dancers. I can only assume that they are playing the music as 'dancers' and not as musicians. I know from my days playing for the morris (I was also a dancer) that I used to play the music as I would have liked to dance it and that, due to the mechanics of the dance, was certainly not 'metronomic'.