One can trace the specifics of various nusachs from older siddurim and machzorim. While they are continually changing as people move around a new shul ends up blending the nusach of various members, it appears that if you time travelled back a millenium you would not find it horribly different, and that probably holds true even if you went back to the period immediately after the destruction of the Second Beit ha-Mikdash. Things get added (e.g. Lecha Dodi) and things get rearranged (e.g. the Hasidic nusach which borrowed some things from the Sefardim via the Ari’zel), but you would get used to it. If you don’t get flustered switiching between yeshivish/Litvish, Hasidic and German (or even various non-Ashkenazi nusachs), you wouldn’t get flustered by the nusachs you would have encountered during the early middle ages.
Melodies probably evolve faster, since they are not written down, but that also means there is no way to trace their development.