To celebrate the Boston Camerata's 50th birthday, the City Council officially proclaimed Saturday ''Boston Camerata Day." The city has abundant reason to be proud of this renowned ensemble; the group's way of celebrating was to perform its ''Carmina Burana" program for an enthusiastic Jordan Hall audience at the Boston Early Music Festival.
Camerata artistic director Joel Cohen put together this program 10 years ago, recorded it, and toured it widely. It was good to hear it again. Cohen noted that some of the medieval texts are famous through Carl Orff's perenially popular and ''raunchy" oratorio. His own effort was to reconnect the lusty poems to their original music or to suitable music of the period.