As I’ve said here many times before, my own playing is a product of how I was taught. My mentor/teacher (I don’t think he ever asked for any money for teaching, he just loved the music and was happy to pass it on) never played anything the same way twice, and would probably be hard-pressed to do so, because it would require him to remember to remember the way he played everything the first time!
He would say “better to learn 20 ways to play one tune, than to learn 20 tunes”. He would teach me a basic version, and then say “you have the tune, now let’s f**k with it” meaning it was now time to explore dozens of different ways of playing it.
So from the very beginning the malleability, the plasticity, of Irish dance music was ingrained in me.
He once heard me playing on the radio and later expressed disappointment that I was being too conservative, not pushing the tunes to the wild edge that was always part of his own playing.
What I gathered from him, and from my own anal overly-analytical study of top traditional players, was that Irish reels and jigs are created more or less on the fly by the player grabbing members of families of building-blocks. Each member of a building-block family equally suits a given rhythmic/harmonic situation (in other words no one member is any more “right” than any other). So it’s not like “theme and variations” but rather very much like how we grab words and assemble them into phrases when we speak. There are hundreds, perhaps thousands, of different ways we could express even very simple notions in English. There is no “one, correct way” but rather any way that does the job is as “right” as any other, though some ways are more elegant, some more clumsy.
“I’m heading off to the market now… is there anything you need?”
“I’m going to the market, can I pick you up anything?”
“I’m off to the market, did you want me to get you anything?”
Which is “the real phrase” and which are “the variations”? None, and none… language doesn’t work that way.
Irish reels and jigs are exactly like that.
There’s something gained, but also something lost, when sessions or performance groups iron out a consistent version of a tune and all play in homophonic lockstep… what is lost is the wonderful chaotic Dixieland-like heterophonic wildness.
http://en.wikipedia.org/wiki/Heterophony
As far as strategies go, it comes from learning the building-blocks and getting them all “under the fingers” so that you can grab them as you go.
Not on whistle, but on pipes, here’s a little video I did a while back showing a large number of different “building blocks” which can be used in the opening phrase of The Earl’s Chair (and of course any other tune whatever that has a phrase like that in it somewhere)
http://www.youtube.com/watch?v=X6fmINqse5Y
I did a whistle video too but it disappeared…