What contemporary traditional musician (if that's not a contradiction in terms) hasn't benefitted from being able to examine the roots of the music he or she is playing. Whether it's a book or recording, its vital to see where our music is coming from. A recording of a song can be viewed as the painting or as the canvas. It is part of the ongoing process of evolution that keeps a tradition alive. There are wonderful renditions being played today of music that would have been long since forgotten if they hadn't been saved on some lasting media. In Irish music, for example, Both Chief O'Niell and Michael Coleman are gone but new musicians are still learning the tunes that O'Niell printed and that Coleman recorded. Not note for note and ornament for ornament, but with the new life that comes from being played by new people. Ironically when the Coleman 78s were recorded, he was criticized for causing too much progress in that the recorded format was deemed a threat to regional styles of playing.
We play old types of music. If our predecessors hadn't collected our roots for us, we wouldn't have any music to worry about to begin with. And truth be told, if you listen to some of the old material that's out there, I'm not sure we've benefited by the tradition going forward. A lot of the "progress" can be better described as degeneration.
I really like McGrath's "seed bank" analogy. I wish I had thought of it.

My $0.02,
Rich