Gone are the days when the airwaves were open to gifted folk-pop eccentrics like these Quebecers, but the spidery-voiced sisters sing on in Matapedia, their homemade music at once rough-hewn and fragile. ''Jacques et Gilles'' is a beautiful, sad song about migrant work; ''Going Back to Harlan,'' a declaration of love for Anglo-Appalachian ballads. Every Kate and Anna McGarrigles song is its own complex world, like the explosions of frost on a winter window. B+

