BOCA RATON — Under a new name, and with its new permanent director, Alexander Platt, at the helm, Boca’s large chamber orchestra demonstrated great subtlety and finesse in an ambitious program in November that included beautiful readings of Bach’s O Mensch, bewein dein Sonde gruss in an arrangement by Max Reger, Mahler’s Bach suite, and the first persuasive rendition I’ve heard in years of the Reformation Symphony of Mendelssohn. Roberta Rust was a fine soloist in the Schumann Concerto, and overall, this concert showed that this group has made real progress since its founding.