CAMBRIDGE - In 1610, when he was 43, Claudio Monteverdi’s “Vespro della Beata Vergine’’ burst over Italy like Kepler’s Supernova of six years earlier, securing him the position of maestro di cappella at St. Mark’s in Venice. In 1640, the composer was 73, and about to scotch any thought he might be ready for the glue factory with the publication of his massive compilation “Selva morale e spirituale.’’ In homage to this later Monteverdi, the Green Mountain Project has assembled a “Vespers of 1640,’’ which it presented Saturday evening in a stupendous performance at St. Paul Church in Harvard Square.
GMP is just two years old, having debuted in January 2010 with a justly (to judge by the now-available CD) acclaimed performance of Monteverdi’s 1610 Vespers. But headed by artistic director Jolle Greenleaf, who directs the NYC-based Tenet ensemble, and music director Scott Metcalfe, of the local a cappella group Blue Heron, and drawing on both outfits for performers, this supergroup has impeccable credentials. For its reconstructed Vespers for the Feast of the Conception of the Blessed Virgin, it chose from Monteverdi’s less familiar compositions, along with the “Ave maris stella’’ from the 1610 Vespers, to which it added a few works by Giovanni Gabrieli, who died 400 years ago, and the Benedictine nun Chiara Margarita Cozzolani.
Blue Heron sings with the tongues of men and women rather than angels, and that’s also true of GMP. Every syllable is clearly enunciated; every word is felt. You could hear the urgency in the “festina’’ (“make haste’’) of Cozzolani’s “Domine ad adiuvandum me festina’’; none of the humanity was leached out. Zachary Wilder gave a bosky splendor to the “O quam pulchra es’’; Sumner Thompson brought power and passion to the “Salve o Regina’’; Greenleaf and Molly Quinn were sister-like in the “Sancta Maria, succurre miseris.’’ The audible interplay of voices with the variously deployed instrumental forces - two cornetti, five sackbuts, three violins, two theorbos, and organ - was a continual delight.
Cutting the richness of the psalms and motets were the plainsong antiphons, which were chanted from all over the church: behind the confessional, up in the organ loft, under the Advent wreath. Metcalfe sometimes conducted the ensemble, playing the violin and using his bow as a baton, and sometimes just sat and listened. The “Ave maris stella’’ was slow and sumptuous, a guiding star. Gabrieli’s concluding “Magnificat’’ exploded like the closing volley of fireworks on First Night.