This article: Bach structured the cantata in eight movements: an instrumental sinfonia and seven vocal movements corresponding to the stanzas of the hymn. The duration is given as 22 minutes.The title of the original parts of the first Leipzig performance is (in Johann Christoph Altnickol's handwriting): "Feria Paschatos / Christ lag in Todes Banden / a.4. Voc: / Cornetto / 3 Trombon. / 2 Violini / 2 Viole / con / Continuo / Di Sign. Joh.Seb.Bach", In this late version, Bach scored the work for four vocal parts (soprano (S), alto (A), tenor (T), and bass (B)), and a Baroque instrumental ensemble consisting of strings, brass and continuo. The brass parts, a choir of cornetto (Ct) and three trombones (Tb) playing colla parte with the voices at times, may have been added in the 1720s. They may also possibly represent the original scoring, in the style of the 17th-century polychoral tradition.The scoring of the cantata Christ lag in Todes Banden has been described as "archaic" and its style "medieval": The string section consists of two violin parts (Vl) and two viola parts (VA); this indicates an older practice as for instance found in 17th-century church cantatas by Bach's ancestors (see Altbachisches Archiv), and in Jesus Christus ist um unsrer Missetat willen verwundet, a Passion setting from the early 18th century (or older) which Bach had performed a few years after composing the cantata Christ lag in Todes Banden. In the first half of the 18th century the standard for a string section soon evolved to two violin parts, one viola part and continuo. The cornett used in the cantata was an instrument that belonged to an earlier age: by the second quarter of the 18th century it had almost entirely disappeared from Bach's compositions. The brass instruments were only used for the 1 April 1725 version of the work.  The other performances (24 April 1707, 8 April 1708, and 9 April 1724) were performed without brass instruments (i.e., Cornetto and three Trombones). The first version (1707 and 1708) concluded with the words of... contains an answer for the question: The brass instruments were only used for the 1 April 1725 version of what?, what is it ?
Answer:
Christ lag in Todes Banden