Complex sentence: The song played over the end credits, "The Rains of Castamere", was adapted from the "A Song Ice and Fire" novels by the American indie rock band "The National", and is sung by their vocalist Matt Berninger.
Split into simpler sentences: The song played over the end credits, "The Rains of Castamere", was adapted from the "A Song Ice and Fire" novels. Performed by the American indie rock band "The National", it is sung by their vocalist Matt Berninger.