Bohemian-born Baroque composer, Jan Dismas Zelenka (1679 --1745) and his music have been little known until recently. During his career in Dresden as a court church composer from 1710 until his death in 1745, Zelenka composed over150 sacred choral compositions.The three masses in the collection entitled Missae ultimae (ZWV 19 -- 21) were written toward the end of his life, between 1740 and 1741. Like his other masses, these three are cantata masses, in which the texts of the mass ordinary are divided, and set as separate movements.In each movement of each mass, Zelenka uses various forms, and compositional techniques in two different styles. Some movements are written in stile antico featuring imitative or fugal techniques. Other movements are written in stile moderno, and can be divided into two categories: choruses with orchestral ritornellos, and arias for solo voice or soli voices. Of great interest, however, is the skill with which Zelenka uses these two different styles within a complete setting of the mass ordinary, or even within single movements, creating stile misto in Missae ultimae by matching specific musical approaches to the character of the different texts.I will first discuss various musical forms and styles in the three masses of Missae ultimae. In Chapter 4, I will focus on the first mass, Missa Dei Patris (ZWV 19), since this work shows more stylistic contrast between movements than the other two masses. In Chapter 4, I will outline the compositional techniques of each movement. For the sake of consistency, the titles of each movement have been capitalized as published in Das Erbe Deutscher Musik -- Bands 93 (1985), 100 (1989), and 101 (1989) -- of Breitkopf und Hartel.