The Washington Bach Consort has been putting on not-to-be-missed performances of baroque music here for decades; little wonder that its large and devoted audience turned out in droves on Sunday for the opening of the group’s 34th season, packing the National Presbyterian Church to its sleekly modernist gills. And as expected, Music Director J. Reilly Lewis put together an insightful program, starring a little-known Mass by Domenico Scarlatti that turned out to be one of those where-have-you-been-all-my-life gems.

The drawbacks of the huge space, alas, quickly became apparent. The consort is an almost intimate group that plays on quiet, rather delicate period instruments, and as Bach’s Concerto in C Minor for Oboe and Violin began — with oboist Geoffrey Burgess and violinist Andrew Fouts in the key roles — the players were swallowed whole by the church’s cavernous acoustics. Burgess and Fouts fought gamely, but Bach’s crisp and detailed counterpoint deliquesced into a soggy wash of pastels — not unpleasant, but probably not the effect the ensemble was after, either.

The acoustics proved a bit more more forgiving with vocal music, and Bach’s Cantata “Aus der Tiefe rufe ich” received a moving and often dramatic performance, thanks in large part to baritone Richard Giarusso, whose expressive and perfectly controlled voice was focused to a laserlike sharpness. A powerful account of Handel’s stately “Dixit Dominus” closed the program, providing the meatiest fare of the afternoon, with the honey-voiced lyric soprano Rebecca Kellerman Petretta providing ethereal touches.

The most seductive music of the day, though, may have been the “Missa Breve, La Stella” by Scarlatti, a composer known for his hundreds of short and often edgy keyboard sonatas. It’s an extraordinarily beautiful work, full of emotional subtleties, and it was clear from his reading of it that Lewis loves this music deeply; it was a performance so tender you never wanted it to end.

Brookes is a freelance writer.