This series at Pace University, started last year by the veteran impresario Matthew A. Epstein, has already been a valuable addition to the vocal scene. This season's first concert, on Sunday, features the potent combination of the soprano Julia Bullock, a star at the Juilliard School in recent productions of Massenet's "Cendrillon" and Janacek's "The Cunning Little Vixen," and - as late replacements for the tenor Joseph Kaiser - the tenor Paul Appleby and the baritone Andrew Garland, all accompanied by the pianist Steven Blier.