Sentence:  Feeling his <WSD>vonce</WSD> before the soulfully enspirited Baltimore congregation, Gordon counts off the tempo for “Blues Up and Down,” the ritualistic set-closer, “roaring out the blocks hotter than a bowl of three-alarm chili, expatiating inventive verse after verse until the total rings up to an astounding 40,” in the words of Hollis. 
Meaning of the word marked with <WSD> tags:  (jazz) A state in which the musician produces great improvization intuitively.