When MusicSource’s Laurette Goldberg founded Philharmonia Baroque Orchestra in 1981 and snared the spirited Nicholas McGegan as music director, she gave the community a priceless gift. Where else can you hear the rainbow colors of baroque instruments illuminated with such elegance and feeling? Nic and such superb PBO musicians as violinist Elizabeth Blumenstock are prized worldwide, in demand as much for the depth of their musicianship as the sheer delight with which they convey its pleasures. The ensemble’s guest soloists and conductors are equally world-class. When not playing in Philharmonia Baroque, the bulk of the musicians are soloists in countless smaller baroque ensembles, members of San Francisco Opera Orchestra, or grooming the next generation of early-music performers. PBO’s history boasts numerous world premieres and ongoing collaborations with the Mark Morris Dance Group, with joint performances of Handel, Purcell, and Rameau in the Bay Area, Los Angeles, and New York. No one would wish to be without American Bach Soloists or Magnificat, both of which frequently mount presentations of equal caliber, but Philharmonia Baroque remains the ensemble that keeps the Bay Area at the forefront of the early-music scene.