Only Cocteau Twins could make “Frosty the Snowman” ecstatic and iridescent. The band's rare cuts flesh out their tantalising, ever-evolving sound, as do singer Elizabeth Fraser's spellbinding guest appearances. On Dif Juz's “Love Insane” she drops to a barely-there coo, while This Mortal Coil's “Another Day”—a companion piece to the better-known “Song to the Siren”—showcases her plaintive side.