The best chamber music performances often convey the impression of a conversation among friends. Sometimes one party commands the discussion, at other times someone else takes charge, but everyone seems fully engaged no matter who has the floor. Hearing the Baroque chamber ensemble La Monica in performance Saturday at Berkeley's St. John's Presbyterian Church was like witnessing an extended dialogue, one whose subject matter might be unfamiliar but that nonetheless left you enthralled. Perhaps the best interpretation of the occasion would be a reunion of old friends, since the program of 17th-century Italian repertoire, "The Amorous Lyre," comprised the original pieces that first brought these performers together while studying at the University of Southern California. But if this conversation had several participants, the main subject focused on a single topic: Tarquinio Merula, a versatile composer of keyboard, instrumental, and vocal music whose works occupied nearly the entire program. Despite this consistency the program never sounded repetitive, thanks to the great variety of instrumental and vocal combinations on display. That this ensemble of just seven players can produce so much variety in sound, textures, and dynamics was perhaps the evening's greatest achievement. Several pieces based on recurring ground-bass patterns showcased La Monica's impressive versatility. Merula's Ciaccona featured violinists Tekla Cunningham and Susan Feldman in the first of many displays of virtuosity. The striking contrast in tone between these players — Cunningham possessing a brighter sound, Feldman a far more mellow tone — only enhanced the sense of textural variety that characterized the program as a whole. The Passacalio by Biagio Marini was a moodier piece, its slow tempo and elongated melodies giving the impression of unfathomable sorrow in La Monica's captivating performance. Many of La Monica's repertoire choices sought to accentuate dramatic characterizations. The jaunty rhythms of Merula's Ballo detto pollicio slowed suddenly before the ensemble gradually accelerated to a rousing close, while the Canzona la fontana found the ensemble in undulating ebb and flow patterns, instruments alternately rising forward and receding into the background. In both cases, the ensemble's irrepressible energy and pitch-perfect timing proved a winning combination.