What repeats the first measure of the fanfare motif on the word "Erschallet"?
"Erschallet, ihr Lieder" (literally: sound, you songs) is a festive concerto, marked Coro by Bach. Words and music are possibly based on an earlier lost secular Glückwunschkantate (congratulatory cantata). A printing of Franck's works contains a cantata for New Year's Day, Erschallet nun wieder, glückwünschende Lieder (Sound again, congratulating songs) that may have served as a model. The movement is in da capo form: the first section is repeated after a contrasting middle section. It is scored for three "choirs": one of trumpets, another of strings and bassoon, and a four-part chorus. The number three, symbolizing the Trinity, appears again in the 3/8 time signature and in the use of three trumpets. The first part opens with trumpet fanfares, alternating with flowing coloraturas in the strings. The voices enter as a third homophonic choir. They repeat the first measure of the fanfare motif on the word "Erschallet" (resound!), as the trumpets echo the motif. The voices repeat the motif from the second measure of the fanfare on "ihr Lieder", and the trumpets echo it again. The chorus repeats measures 3 and 4 on "erklinget, ihr Saiten", commanding the strings to play. As a culmination, the first syllable of "seligste Zeiten" (most blessed times) is held on a seventh chord (first in measure 53), during which the instruments play their motifs.In the middle section in A minor the trumpets rest while the other instruments play colla parte with the voices. Polyphonic imitation expands on the idea that God will prepare the souls to be his temples. The first sequence progresses from the lowest to the highest voice, with entrances after two or three measures. The highest voice begins the second sequence, and the other voices enter in closer succession, one or two measures apart. Gardiner interprets the polyphony as "conjuring before us the elegant tracery of those 'temples' which God promises to make of our souls". The first part is repeated as da capo.The movement is comparable to the opening of Tönet, ihr Pauken! Erschallet, Trompeten! BWV 214 (Resound, ye drums! Ring out, ye trumpets!) composed in 1733 on another text calling instruments to sound, which Bach later used with a different text to open his Christmas Oratorio. Bach used a festive scoring with three trumpets in triple meter in his 1733  Missa for the court in Dresden, in the Gloria, in  contrast to the preceding Kyrie.
voices