The choir I have the pleasure of being a member of is giving a free concert on July 1st in Strasbourg, the evening of the ESC BBQ.
The (short) Mass was composed for 2 organs and 2 choirs. You can hear samples (by other choirs of course) on YouTube to give you an idea. It is very beautiful and there will be lots of other very good pieces, instrumental as well as the choir singing a capella. The organist is a famous one.
Please come and enjoy!