CAMBRIDGE - When in 1863 word started to leak out that Gioacchino Rossini, 30 years retired from opera composition, had written a choral mass, it was the Second Empire equivalent of a Beatles-reunion rumor.
Speculation reached America; a New York magazine wondered, "Is it a requiem, and for whom is it destined?"
As the Masterworks Chorale showed on Sunday, Rossini's "Petite Messe solennelle" is hardly a requiem (though it was destined for Rossini's bankers), but a quirky stylistic mix, in which Rossini's operatic flair is sometimes an enhancement, sometimes a non sequitur. And sometimes, the performance seemed caught between the two.
Much of the first half was faint-hearted, as if the group were wary of the more secular inspirations.
Rossini's original chamber accompaniment of two pianos (Leslie Amper and Randall Hodgkinson) and a reedy harmonium (Kevin Galié), caught the spirit, enthusiastic and a little melodramatic, and Masterworks director Steven Karidoyanes has trained his charges well: The choir made a terrific sound at full volume, rich and precise.
But in quieter passages, presence and energy dissipated. The solo and ensemble movements comprising the "Gloria" all converged on the same stately tempo; the music could have used more blasphemous excesses of drive or languor.
Tenor Martin Kelly was miscast, with a lean, sometimes muscular tone in a part calling for Italianate honey, but his musical instincts were sure, committed to the jaunty "Domine Deus" movement's incongruous, blustery triumph. Baritone Marcus DeLoach was an excellent preacher, bringing a sonorous tone to a "Quoniam" in which Rossini mischievously sends the singer into basso depths on the words "tu solus altissimus."
In the second half, things picked up markedly. The a cappella "Sanctus" had moments of thrilling full-throated contrast. Soprano Meredith Hansen sang the surprisingly sweet "Crucifixus" with a creamy tone and soared in the "O salutaris hostia."
Mezzo Rebecca O'Brien was darkly dramatic in the final "Agnus Dei"; behind her, the ensemble's diffuse softness became an asset, suggesting Verdi's offstage choirs.
The afternoon's best moments came where caution and ecclesiastical propriety were thrown to the wind. As the choir coursed home in the "Credo," a typically Rossinian musical engine running on no other fuel than its own self-evident pleasure, one realized the setting was, for once, exactly right. On the text "vitam venturi saeculi," the life of the next world, Rossini fashioned his own idea of heaven: a perpetual operatic finale ultimo.