Surely one of the great joys of being a music-lover in the present day is our rediscovery of French Baroque opera—not to mention the Italian and German masterpieces with which the Boston Early Music Festival has regaled its audiences over three decades. The amazing resurrection of Les Arts Florissants' legendary 1985 production of Lully's Atys this year brought that home. (They are now available on DVD and Blu-Ray.) BEMF had produced Rameau's Zoroastre in 1983. After that 18 years passed until they returned to French opera in their 2001 production of Lully's Thésée, followed by Psyché in 2007. While these four represent the most public strain of opera in Paris, the grand spectacles produced either under royal patronage or at the Opéra, BEMF's chamber opera series has provided a window on the smaller-scale, more private sort of performances cultivated by Marie de Lorraine, the Duchesse de Guise, with music by her house composer, Marc-Antoine Charpentier.