Daniel Abraham led the Bach Sinfonia in works by Handel, Corelli and Torelli. (David Stuck)

With the nimbleness of the free-form organization that it is, Daniel Abraham’s Bach Sinfonia can assume many guises. It has performed as a full-blown Baroque orchestra with soloists and chorus, as a medium-size Baroque chamber orchestra and, as it did on Saturday at the Silver Spring Cultural Arts Center, as an octet — Baroque, of course, to the core. Abraham, who has a gift for programming early music, manages to plop his elegant selections down into a sort of casually intimate “aw, shucks” atmosphere with comments about the music that seem so off-the-cuff and unpremeditated that they hide the scholarship behind them.

What made this evening special was the performance of soprano Nola Richardson, who blew through the runs of the aria “Rejoice Greatly” from Handel’s “Messiah” at Abraham’s fast pace with astonishing balance and accuracy, lavishing crystalline diction on everything she touched and managing, throughout, to shape phrases with natural-sounding ease. Equally astonishing was the performance of Stanley Curtis, who performed miracles on his valveless Baroque trumpet, rolling out long high trills, wide octave leaps and the sort of chromatic lines that shouldn’t be possible on that instrument. With its almost human sound the product of its small bore, his trumpet is an ideal vocal partner and, together, Curtis and Richardson gave terrific readings of Handel’s “Let the Bright Seraphim” and Bach’s cantata “Jauchzet Gott.”

The purely instrumental parts of this Christmas program were two “Christmas” concerti grossi — Corelli’s, chipper and well known; Torelli’s, somber and less familiar — and the “Pastoral Symphony” from “Messiah,” played fast enough to resemble the dance it ought to be. Both concerti grossi were for two solo violins which, in these performances, never quite managed to assert their solo-ness even through the light, Baroque-bowed textures of the ensemble. There were times when the octet struggled to find its footing at the beginning of pieces, and the Sinfonia needs to find a larger, more assertive-sounding harpsichord if the instrument is to contribute at all to the ensemble, but individual performances, particularly from continuo cellist Douglas Poplin, were outstanding.

Audience participation in two sets of period carols was both eager and well-schooled.

Reinthaler is a freelance writer.