As a player who, early on, eschewed training in the name of spontaneity and authenticity, put me down solidly on the side of training. No amount of “soul” can entirely substitute for technique. To perform with feeling and authenticity requires immersing one's self in the target idiom until all it's nuances and feeling and possibilities have been explored and, dare I say, grokked. Learning to listen is at least as difficult as learning to perform.

Once an idiom has been made “one's own,” the more technique the performer has at hand, the better and more interesting will be the performance. Dizzy Gillespie, Charlie Parker, et al., created bebop, in part, from the difficult exercises they were playing in order to improve their technique. Bebop is thought of as an impromptu form but being steeped in the idiom is, by itself, definately insufficient to enable its performance.

Folk and traditional forms may not be as demanding as bebop but even the unaccompanied Appalachian singer is employing rather precise technique that, if not well mastered, betrays the performer as second rate. To a listener with modern urban sensibilities, the technique may not be apparent but it is none the less important to the performer's intended audience.

But that's just my opinion, yours may be different.

      - Mark