I absolutlely fell in love with the Michael Hadyn Missa Sancti Joannis Nepomuceni a couple years ago. The piece would likely work well with organ alone, or with organ two violins and cello (as we did it). I assume there may be trumpet and timpani parts if you have them. Since it was written for the Salzburg Cathedral, there are no viola parts.

Now, I did this for the Easter Vigil a couple of years ago (and my score's not handy at the moment), so we didn't do the Kyrie or Credo -- so there may be solos in there, but if there are any solos in the Benedictus, they weren't particularly soloistic in quality, so I just had the section sing them, and it worked to good effect.

Two clever things about the piece. For those who don't know, Michael Haydn (like Mozart for a time) worked for Archbishop Colloredo, who liked his Mass *short* - so M. Haydn himself marked optional cuts(!) in the score, presumably for use at Mass when celebrated by the archbishop, and ignored otherwise.

I also love that the 3/4 Hosanna theme - which is quite lyrical (and feels like it may have been lifted by some film composer) returns in the Benedictus in 4/4 - which I don't know I've seen anywhere else.

It's published by Carus, but worth it. Maybe not a gem for the concert hall, but definitely for use in the liturgy if you're going to do a Classical-era Missa brevis.

*** Sorry, just read you were looking for only the Gloria. I don't remember there being solos in there, but I will check when I get to the office later this morning.

Another composer - Johann Nepomuk Hummel: Mass no. 1 in B-flat and Mass No. 3 in D, both with well-matched organ parts (or orchestra).

Thank you both VERY MUCH. This is what I was looking for.