One feature that is especially prominent in this period is the frequent presence of ostinato bass as the basis of variation forms.

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).

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. 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. 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. 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. 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. The name was appropriate, for none of the composers on the program counts as well-known. 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. 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.

“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.

Amadine sectional