Incidentally, I was listening to the Köln concert as I read this. I laughed out loud.
Or a huge number of jazz musicians in general. In the jazz courses I took in college is was part of the training.
Really? What professional pianist besides Jarrett has audible vocalizations on their recordings?
Here's a segment of Billy Taylor where you can here him (and almost every time you can see his lips you can see him scatting along) from an incredible series called The Subject is Jazz