Cocteau Twins’ EPs are as groundbreaking as their albums, which makes the Lullabies to Violaine anthologies essential to understanding the arc of their career; Volume 1 covers 1981 through 1990. The searing “Feathers Oar-Blades” retraces their all-but-forgotten post-punk roots, while “Sugar Hiccup” highlights their exquisite balance between cutting guitars and dreamy atmospheres. By “Iceblink Luck,” Elizabeth Fraser’s vocals have become more ornate and the songwriting more elaborate; the band tests the boundaries of pop music without sacrificing any of their dark magic.