CAMBRIDGE -- Maybe it was the repertoire. Maybe it was the presence of a soloist. Maybe conductor Gisèle Ben-Dor has a twin. Whatever the reason, Sunday's performance by the Pro Arte Chamber Orchestra at Sanders Theatre might have been by two different ensembles. Intermission, normally a pause, was in this case a demarcation.
In the first half, Eliot Fisk was the guitarist in Heitor Villa-Lobos's 1951 Concerto and the premiere of Fisk's own arrangement of Mark O'Connor's "Winter," the final movement of "The American Seasons," a 1999 violin concerto. Ben-Dor, Pro Arte's conductor emerita, led both numbers with a muscular, emphatic beat. In the Villa-Lobos, music of episodically fragmented Brazilian charm, the resulting boxy phrasing precluded any badinage between soloist and orchestra. The O'Connor work, mixing jigs and breakdowns in interlocking, gently clashing counterpoint, was heavy on its feet: The polyrhythms wrestled with the meter instead of dancing on top of it, and the overall texture lacked the transparency needed for O'Connor's busy fugues.
Fisk, though, was masterful, with the flair that separates the true virtuoso from a mere technician, tossing off fiendish runs with theatrical aplomb. His transcription of O'Connor's fiddle-derived showpiece fully came into its idiomatic own in an extensive cadenza, evoking everything from Irish reels to Scruggs-style banjo to the work's Vivaldean inspiration.
After intermission came music of Mexico's Silvestre Revueltas and his Argentinian counterpart Alberto Ginastera, composers who, along with Villa-Lobos, Ben-Dor has long championed. With the opening bars of Revueltas's "Homenaje a Federico García Lorca," written in 1936 -- just after Lorca's assassination -- she was at once more relaxed and more in command than at any time in the first half. It's an extroverted, sparklingly dissonant riot of popular and folk tunes that only hints at its tragic subject in a pensive middle interlude. Color and drama flowed through the ensemble.
Likewise in Ginastera's 1953 "Variaciones Concertantes," 12 elegant variations doubling as a mini-concerto for orchestra: The composer's characteristically brief, telling motives viewed from varied contrapuntal and timbral angles shone under Ben-Dor's intuitive direction. Noteworthy among the solo voices were oboist Nancy Dimock and bassoonist Wren Saunders, delicately swaying in canon, and violist Don Krishnaswami, giving his oft-neglected instrument a soulful workout.
Saxophonist Demetrius Spaneas joined the strings for a velvety encore, Astor Piazzolla's refined, melancholy "Oblivion."