Aaron J Rabushka wrote:

>Mozart also used trombones in Idomeneo (for a frustratingly small amount
>of time) as well as the Requiem and several other pieces of church music.
>Gluck used them in Orfeo ed Euridice.  Unfortunately even Vivaldi didn't
>give them a concerto.

Trombones in Mozart era church music served one purpose and one purpose
only, that is, to double and support the male vocal parts given the
shortage of male singers.  This shortage, as I recall was due to the high
number of men involved in military campaigns at the time.  I forget which
war it was, perhaps someone with a little more European history at his
fingertips than I have will fill in the details.

Kevin Sutton