Well there's this thing about taste Marty. Freight Train (and Railroad Bill) have a certain intended sound to them, and i.m.h.o. are meant to be played close to the way their originators performed them. That's part of the allure of those tunes. Again, i.m.h.o. it would not be appropriate to "fancy them up" and alter the basic sound and flow of them. I suppose though you could do it just to check out how they'd sound, but you'd be creating something entirely different than what you started out with. Not necessarily a bad thing, just different, and maybe you'd learn a thing or two in the process. Course this altering of songs and putting our own unique imprint or twist on them, is also how one develops their own "style".

On the other hand, if you were playing something like Doc's "Deep River Blues" there's lots of opportunity for playing around with substitutions, as long as you do it during soloing sections. Hell I even wrote a bridge to it, just so it wouldn't become so redundant playing it over and over again. Here is a prime example of a tune you can take and kind of have fun with it. I mean Doc starts out and plays it pretty straight. Then around the 3rd or 4th pass, he introduces some cool cross picking into it (actually reverse banjo rolls) and then brings it back more simply and then out. I often play this tune with a very typical bluesy ending, following by the Merle chord (I described previously in another post) as the final chord of the song. My peers usually say "very nice" when they hear it.

Certain tunes need to be kept simple. Others lend themselves to "fancying up". Experience, growth as a player, getting together with other players and listening to their ideas, are part of the education and evolution, in determining taste and developing an intuitive sense of how far you can stretch the boundaries of a given song. This is how "innovators" are sometimes born. You need to have a sense of what the rules are in order to learn how and when to break them. *G*