The suggestion of "spontaneous speech" comes from not only a "highly rehearsed" intonation but is perhaps primarily the result of extreme editing, as discussed

The suggestion of "spontaneous speech" comes from not only a "highly rehearsed" intonation but is perhaps primarily the result of extreme editing, as discussed in this revealing audio post looking at the practice by On the Media: http://lk.tumblr.com/post/5435349794/public-radio-production http://lk.tumblr.com/post/5435349794/public-radio-production Really eye-opening to learn that the NPR anchors, reporters, and guest interview subjects are not nearly as quick-thinking and well-spoken as they are made to sound in the final product.