Vivaldi's Kyrie in G minor for double choir and orchestra (RV587)was probably the companion piece to a lost setting of the Gloria in B flat major for which an introduzione survives it dates from the 1720s and opens with a solemn chordal passage from the introduzione I've just mentioned. This response to this is based on on a broken-chord figure on strings and these two musical elements are heard in alternation before Vivaldi combines them at the end of the movement. The second movement the 'Christe Eleison' is a duet for the two choirs of sopranos and altos with strings. The writing is quite florid and I like very much how he echoes it and underpins in the instrumental base. The final movement is an impassioned Kyrie whose choral introduction is followed by a starkly beautiful double fugue for the combined choirs. Enjoy :-).