Kate and Anna McGarrigle: Love Over and Over (Polydor) ***½

WHILE THEIR most compelling virtue is their lovely vocal interplay, Kate and Anna McGarrigle have always been careful to use classy session players. As a result, it sometimes seems as if the sisters are making the point that their mix of church music, ballads and north-of-the-border jug-band fare is not some quaint folkie goulash but a disciplined series of choices. Love Over and Over, with Dire Straits' Mark Knopfler playing perky guitar on the title track, is the Canadian duos most meticulous album yet.