Last weekend it was Mario Venzago employing the Indianapolis Symphonic Choir — and playing Mozart — for the first time. For his annual solo appearance, Indianapolis Symphony Orchestra first violinist and concertmaster Hidetaro Suzuki also joined our new ISO music director. But throughout this rather unusual, religiously inclined ISO Classical Series program, it was the voices that dominated. To start, the 137-voice choir — standing on a specially erected upstage platform — joined a reduced orchestra for Mozart’s Kyrie in D Minor, K. 368a, a setting of the first part of the Catholic Ordinary, and anticipating the timbres of the composer’s late, unfinished D Minor Requiem. This was followed by Te deum laudamus, K. 141, an early, light-veined work belying Mozart’s solemn title, and ending with a well-wrought fugue. As I found nothing to carp at in these two pieces’ execution, I’m obliged to report that conductor, orchestra and chorus combined to bring off their respective roles splendidly. Programmed for the first time in its 74-year history, the ISO — with the choir — gave us Mozart’s Ave verum corpus, K.618, perhaps the most beautifully moving 46 measures in Western music. Furthermore, Venzago, holding his players and his voices in check, gave us such a soft, slow, sublimely exalted five minutes as to practically render the rest of the program of no consequence, in comparison. On a considerably lower plane, we heard, after intermission, Schumann’s rather obscure Nachtlied, Op. 108, a choral work nonetheless worthy in its own right, and very nicely sung and played. It’s regrettable that Suzuki’s playing of and Venzago’s interpretive approach to Mozart’s Violin Concerto No. 4 in D, K.218 proved less successful than the program’s chorus-supplemented offerings. Venzago’s slow, tempo-varied, subdued and seamless approach resulted in imprecise ensemble playing, which threw Suzuki off track, in both pitch and tonal quality, mostly in the first movement. After a rousing, sensitive performance of Ravel’s Daphnis et Chloé Suite No. 2, with a typically lovely Karen Moratz flute solo in the “Pantomime” section and an effectively paced “General Dance,” Venzago left to thundering applause. But I left dwelling only on Ave verum corpus.