The author first discusses the fundamental relationship, in Hebrew writing systems, between script and sound, in particular the investigation of this relationship in texts of the past. In the first major section, an exhaustive description of three texts from around 1600 serves as a fixation point for a presentation, based on some 70 texts, of the development of the writing and sound systems from the oldest texts to the demise of written West Yiddish in Germany around 1800. Main subject of the second major section is the gradual distancing of the German component of West Yiddish from all varieties of German. A comparison of the phonetic system with the other linguistic levels shows that West Yiddish achieved its independence from German most readily at the semantic level, more slowly in phonology. In the final chapter the author tries to organize all observed graphic and phonic speech changes according to a few pragmatically intelligible categories.