This book presents a dynamic account of the phonemic changes between MHG and NHG. The nature of MHG is re-examined by selecting as a basis texts from 1150 to 1270, although reconstructed MHG is also used. As well as standard NHG forty-one dialect mographs are used to show the variety of developments in dialects. The book contains eight maps based on these dialect mographs. The main patterns of phonemic changes are followed though from MHG to NHG using secondary literature to document changes.