I wonder why do we have to add yeast in Sourdough Rye Bread?
I'm starting to move to the Sourdough Rye Breads section on Jeffrey Hamelman's Bread cookbook. After flipping through the recipes, I noticed that Hamelman included commercial yeast in (almost) every single SD rye recipe. The recipes also have short fermentation time, only an hour and doesn't mention anything or offer option of retarding the doughs.
I wonder if yeast is necessary in making rye sourdough? Is rye sourdough suitable for retardation? I searched TFL about this topic and looked briefly on what had been posted. Nothing seems to answer my curiosity.