Generally, for a double premiere, I’d recap both episodes in a single post. But “The Devil’s Chord” is so different from “Space Babies” that it doesn’t feel right to lump them together — we’ve gone from a creature made of baby boogers to a godlike being from another realm who can turn music into a physical weapon. With the help of the Beatles, the Doctor and Ruby must take on Maestro, a child of the elemental force known as the Toymaker. (In case you didn’t catch the 60th-anniversary specials...