Jan Dismas Zelenka, also known as Johann Dismas Zelenka, was the most important Czech Baroque composer. His music is admired for its harmonic invention and counterpoint.
Zelenka’s pieces are characterized by very daring compositional structure, with a highly spirited harmonic invention and perfection of the art of counterpoint. His works are often virtuosic and difficult to perform, but always fresh and surprising, with sudden turns of harmony. His writing for bass instruments in particular is far more demanding than that of other composers of his era.—Excerpted from Wikipedia