Actually T-boy,

I'm partly with with on this - many older simple folk style tunes work well with the I IV V7 (or even I IV V) major chord progressions, so it's often worth trying this progression. It's just that the order of the chords varies for different songs... :-) Many tunes written before the 1960's and 1970's will fit.

And then there is my theory that there are only seven folk tunes - but then I am a Low Whistle player... :-)