"Good improvisation communicates harmonic progression melodically. Effective melodies manipulate harmonic content through the use of guide tones and preparatory gravity notes, masterfully woven in systematic tension, release, and transparent harmonic definition."
We recently shared a terrific Spinal Tap parody in our news column, Spinal Tap on Jazz if you haven't seen it already. As is true with all comedy, there is always a certain amount of truth built into good material, and this is no exception. The aging rockers candidly lament several elements of jazz that even die hard jazzers cannot disagree with.
"The fact is, jazz is mistakes. You're playing it wrong...
Jazz is an accident. Waiting to happen. Glad to have happened..."
Some schools will even give you a degree in it. Making mistakes.
"Miles Davis. He kept putting this thing on the end of his horn--to make it sound less like a trumpet.
What's wrong with him?"
What do we mean about "mistakes?" Consider the "blue notes," the b3, b5, and b7 of the Blues Scale. If your Folk ear were used to nothing but major scales, these notes would sound like mistakes. But does a b5 sound wrong in Leonard Bernstein's "Maria." Sing it in your head, "Mar-i-a." that 2nd syllable is a b5, not part of the major scale, but it does propel the melody. How about the b3 in the beginning of Stormy Weather? Definitely not a mistake.
Probably the biggest grief a jazz musician will take has to do with the notion of playing "outside the changes." The Conflict/Resolution nature of art in general, drama, music, visual arts tests everyone's preconceived notion of just how much "tension" they can tolerate. Playing an improvisation based on scale 1/2 step higher for a few bars and back again, is a very common jazz tool. It's the "intentional" part of that tactic that is called into question. It's not a mistake if it's premeditated and purposeful in creating momentary tension.
This is ultimately the beauty of jazz, that blur between intent and mistake.