A slower crescendo, perhaps, but an equally mighty fortissimo in the end. Take Antonin Dvořák’s Rusalka, an opera (or lyric fairy tale) with an origin every bit as magical as its subject matter. It took seven years for Rusalka to be performed outside the Czech lands, first in Ljubljana. 9, “From the New World,” was taken into space on the Apollo 11 mission, his Slavonic Dances, cello concertos, and string quartets are performed the world over, and his opera Rusalka has at long last entered the standard repertoire. Dvořák’s lyric fairy tale once seemed as if it might disappear in a misty haze, under-appreciated and even persecuted by German chauvinists, Czech communists, and unimaginative foreign audiences.