“Gli Incogniti” is Italian for “the unknown”—which struck me as a startlingly modest name for a performing ensemble until I read the essay in the BEMF program book for the early evening concert given by the group at Jordan Hall on June 14. There I learned that this group, founded in 2006 by violinist Amandine Beyer, prides itself on its investigation of largely unknown instrumental music of the 17^th century. It was a yeasty period in which all kinds of experimentation formed many of the approaches to abstract instrumental music that dominated the period—and, indeed, the centuries to follow.

The name was appropriate, for none of the composers on the program counts as well-known. While a few of them (especially Froberger and Biber) have a reputation among persons with some knowledge of the period, others are all but unknown, particularly Giovanni Antonio Pandolfi Mealli, for whom we have only documented activity with no indication of birth or death dates or much other relevant information.

On this occasion, their first appearance in the United States, Gli Incogniti was made up of four players (depending on repertory requirements, other musicians occasionally perform with them): Amandine Beyer herself, a remarkable French violinist with a flair for expressive flexibility in a framework of rock-solid tuning; Baldomero Barciela, from Spain, viola da gamba, whose continuo line matches Beyer’s in flexibility and verve; and two Italians, Francesco Romano on theorbo and Baroque guitar, and Anna Fontana, harpsichord and organ.

The four are excellently matched in feeling and projecting the often unusual rhythmic gestures of the music from a period that has largely cast off the common 16^th-century manner of creating instrumental music by drawing on the polyphonic and sectional structures of the vocal chanson (turned into the instrumental canzona da sonar) and begun to investigate organizational techniques derived from the dance or newly invented approaches.

Some parts of these works unfolded lines of an almost vocal character, like the free-flowing recitatives of a Monteverdi, alternating with sections of marked rhythmic profile and metrical character. Recitativelike passages were performed by Amandine Beyer, who is truly the animating spirit of the ensemble, with a grace and shapely singing quality that evoked the leading opera singers of the day (or the top modern specialists in 17^th-century repertory), responding to the harmony and line as if projecting deeply felt affect with subtle acceleration and delay, dynamic emphasis, and, at the end, welcome repose. Most spectacular in effect was Biber’s “Sonata violino solo rappresentativa,” where the last word of the title suggests the aim of suggesting programmatic ideas and objects (including birds with actual birdsong, and a musketeer march).

One feature that is especially prominent in this period is the frequent presence of ostinato bass as the basis of variation forms. Both the pieces of Pandolfi Mealli (“La Castella” and “La Cesta,” from his Opus 3 sonatas, published in Innsbruck in 1660) are dominated by such forms, the latter especially striking in descending semitones. I suspect that the names given the pieces were intended as homage to Dario Castello and Luigi Cesti (in the context of such tributes, composers, like ships, become feminine), but so little is known about the composer that it is impossible to be certain whether he had connections with those composers or simply admired them from afar—or, indeed, whether the titles have some other significance. The concluding piece on the formal program was another ostinato work, the Chiacona of Antonio Bertali.

The theorbo player, Romano, and the organist, Fontana, had the opportunity to perform a solo number, one in each half, giving them a chance to step out after providing essentially inner voices for the rest of the program. Romano played a showpiece by Kapsberger (Toccata I from his Libro Quarto of 1640), and Fontana several harpsichord works by Froberger, including Toccata IX and his well-known Lamentation on the Death of King Ferdinand IV.

From beginning to end, to strong expressive effect, the program of Gli Incogniti made the unknown known. I, for one, will eagerly anticipate future visits of this virtuosic ensemble, which seems to have fully absorbed what we now know about the character of 17^th-century instrumental music and found the means to bring it, gloriously, to life.

Steven Ledbetter is a free-lance writer and lecturer on music. He got his BA from Pomona College and PhD from NYU in Musicology. He taught at Dartmouth College in the 1970s, then became program annotator at the Boston Symphony Orchestra from 1979 to 1997.