extemporizer

Richmond Palmer was a tireless extemporizer upon this theme.

"He's the best thinker, best extemporizer.

It was a special work of collaboration between Mingus as extemporizer and Mr. Johnson as interpreter, and it was promising.

He is as intensely figurative a poet as Whitman and Stevens were, and like these ancestors he wears a mask of the casual extemporizer that no reader should trust for an instant.