Jewish statutory prayer is everywhere the same in skeleton, the Shema with its blessings, the Amidah, the public reading of the Torah, and everywhere different in flesh. The wording of the blessings varies in small persistent ways, the poems admitted into the service differ, the order of certain passages diverges, and the melodies belong to each community's own musical dialect. Such a settled configuration is a nusach, and Nusach Ashkenaz is the configuration the Jews of medieval Germany and northern France made and their descendants carried across the world.
Liturgical historians, following the lines drawn by scholarship since Leopold Zunz and consolidated in Elbogen's great history, trace the statutory Jewish rites to two ancient parents, the rite of the land of Israel and the rite of Babylonia, and read Nusach Ashkenaz as the branch that kept the most Palestinian material: readings, wordings and above all the enormous corpus of piyyut composed in the land of Israel and cherished in the Rhineland long after the Babylonian geonim had tried to prune it. The rite's framework was nonetheless the Babylonian order that all medieval Jewry accepted, transmitted through the prayer books of Amram Gaon and Saadia. What the Rhineland added was its own record of custom, minhag, elevated almost to law: books such as the Maharil's fixed not only texts but the very tunes, the mi-Sinai melodies for the Days of Awe that Ashkenazi cantors still regard as untouchable.