So if you imagine that the choice of 2/4 or 4/4 implies any suggestion as to how the music might be played, you would probably be imagining wrong. The only practical difference in this case is that in 2/4 the fast notes are written as semi-quavers, and in 4/4 they would be written as quavers.

Actually I'd disagree with that Greg. The choice of 4/4 rather than 2/4 is doing precisely that, in that is is indicating whether there are an underlying 4 beats to the bar or 2.

I stand by my notation of Soldiers Joy in 4/4 but my other example above, John Ryan's, perhaps better illustrates the point I was trying to make - play John Ryan's with four beats to the bar and the whole feel of the tune is different to playing the same tune with two beats to the bar.

The notation of a trad/folk melody is only the beginning of a fully-rounded performance of that tune, with ornamentation and maybe a few subtle variations second time round, supplied by the experience, skill, and taste of the performer. In that respect the 'dots on the page' are closer to an aide-memoire or a snapshot than a full performing score. I've said it before, and I'll no doubt say it again, that the real art of playing trad tunes from the dots is in playing all the stuff *between* the dots. But one part of the basic framework of a tune that the dots can provide very easily is an indication of the underlying pulse, and that comes from the choice of time signature.