Wotan, Valkyries, Valhalla and the Twilight of the Gods - these words are the very stuff of Wagnerian opera, but their origin in ancient Germanic and Norse mythology is less familiar. Christopher Page looks at poems from the old Icelandic Edda - a collection of stories of giants and dwarves, prophecies and visions - with musical interpretation by the ensemble Sequentia. Repeated from Sunday 3.15pm