Pumpernickel bread that came to be known as "Pumpernickel", Westphalian pumpernickel is distinguished by use of coarse rye meal and a very long baking period, which gives the bread its characteristic dark color. Like most traditional all-rye breads, pumpernickel is traditionally made with an acidic sourdough starter, which preserves dough structure by counteracting highly active rye amylases. That method is sometimes augmented or replaced in commercial baking by adding citric acid or lactic acid along with commercial yeast. Traditional German pumpernickel contains no coloring agents, instead relying on the Maillard reaction to produce its characteristic deep brown color, sweet, dark chocolate,
What Is and What Should Never Be descending riff [of "What Is and What Should Never Be"] is amazing: It's like a bow is being drawn back, and then it releases. The rhythm of the vocals is almost like a rap. It's insane — one of their most psychedelic songs." This was also one of the first songs recorded by the band for which Robert Plant received writing credit. According to rock journalist Stephen Davis, the author of the Led Zeppelin biography "Hammer of the Gods: The Led Zeppelin Saga", the lyrics for this song reflect a romance Plant had with his wife's younger sister. "What Is