What was the name of the person who eliminated the organ continuo, added parts for flutes, clarinets, trombones and horns, recomposed some passages and rearranged others while writing small scale performances of Messiah?
During the 1750s  Messiah was performed increasingly at festivals and cathedrals throughout the country. Individual choruses and arias were occasionally extracted for use as anthems or motets in church services, or as concert pieces, a practice that grew in the 19th century and has continued ever since. After Handel's death, performances were given in Florence (1768), New York (excerpts, 1770), Hamburg (1772), and Mannheim (1777), where Mozart first heard it. For the performances in Handel's lifetime and in the decades following his death, the musical forces used in the Foundling Hospital performance of 1754 are thought by Burrows to be typical. A fashion for large-scale performances began in 1784, in a series of commemorative concerts of Handel's music given in Westminster Abbey under the patronage of King George III. A plaque on the Abbey wall records that "The Band consisting of DXXV [525] vocal & instrumental performers was conducted by Joah Bates Esqr." In a 1955 article, Sir Malcolm Sargent, a proponent of large-scale performances, wrote, "Mr Bates ... had known Handel well and respected his wishes. The orchestra employed was two hundred and fifty strong, including twelve horns, twelve trumpets, six trombones and three pairs of timpani (some made especially large)." In 1787 further performances were given at the Abbey; advertisements promised, "The Band will consist of Eight Hundred Performers".In continental Europe, performances of Messiah were departing from Handel's practices in a different way: his score was being drastically reorchestrated to suit contemporary tastes. In 1786, Johann Adam Hiller presented Messiah with updated scoring in Berlin Cathedral. In 1788 Hiller presented a performance of his revision with a choir of 259 and an orchestra of 87 strings, 10 bassoons, 11 oboes, 8 flutes, 8 horns, 4 clarinets, 4 trombones, 7 trumpets, timpani, harpsichord and organ. In 1789, Mozart was commissioned by Baron Gottfried van Swieten and the Gesellschaft der Associierten to re-orchestrate several works by Handel, including  Messiah (Der Messias). Writing for a small-scale performance, he eliminated the organ continuo, added parts for flutes, clarinets, trombones and horns, recomposed some passages and rearranged others. The performance took place on 6 March 1789 in the rooms of Count Johann Esterházy, with four soloists and a choir of 12. Mozart's arrangement, with minor amendments from Hiller, was published in 1803, after his death. The musical scholar Moritz Hauptmann described the Mozart additions as "stucco ornaments on a marble temple". Mozart himself was reportedly circumspect about his changes, insisting that any alterations to Handel's score should not be interpreted as an effort to improve the music. Elements of this version later became familiar to British audiences, incorporated into editions of the score by editors including Ebenezer Prout.
Mozart