A touch of Appalachian spring can sometimes be heard amid the Balkan melancholy, wiry rhythms and whirling dance steps of Harmonia. The Cleveland band, founded by third-generation American Walt Mahovlich of Hungarian-Croatian heritage, makes no bones about ethnic purity. Surely he heard American music amid the Slavic sounds of ethnic Cleveland. And yet, the DNA of the ancient Celtic ballads that crossed the Atlantic with the early settlers and the Old World music that followed centuries later contain common strands. Harmonia has also grown from an infusion of more recent Eastern European immigrants to Cleveland, trained in East Bloc conservatories and with a different perspective than Mahovlich's grandparents. The merger of liveliness and sadness is invigorating, whatever the source.