And of course, even if he wasn't Catholic, it is not at all unusual for a composer to write a Mass--it is one of the essential musical forms to master, of course. Well below is a video of his "Hope! A Celebration Mass", as performed in Russia. Jazz-wise: I love it. It sings and zings. And, oh, Dave is having so much fun up there--the kind of fun we had in high school when we got to sing a really fast exciting Christmas carol at Mass. I love it! But it seems more appropriate as a concert piece than a part of an actual Mass. (But then, so does Mozart's Requiem.) And anyway, not all religious art needs fit in with the actual worship and liturgy of the Church.
I wish I knew which part of the Mass this was. It is in Russian, so I can't tell. It seems like a Gloria, given its triumphant nature.