Of all the Jewish rites, the eastern Sephardic liturgy stands closest to the oldest complete prayer books in existence. The order of Amram Gaon in the ninth century and the siddur of Saadia in the tenth were composed in the academies of Babylonia for communities that asked how to pray, and the rite of the eastern communities descends from their answers with fewer detours than any other.
The Spanish exile of 1492 folded the developed liturgy of Sepharad into the existing communities of the Ottoman world and North Africa, and the two streams, Babylonian foundation and Iberian superstructure, fused over the following centuries into a broadly common eastern rite. The third layer is mystical. The kabbalah of Isaac Luria, itself built on Sephardic prayer, flowed back into the eastern synagogues through Safed, and its usages, the meditative preambles, the Psalm sequences, the wordings adjusted to kabbalistic doctrine, were given halakhic authority for the East by Yosef Hayyim of Baghdad, the Ben Ish Hai, whose homiletic code of that name remains a household book in Sephardic homes.
The nineteenth-century printing presses of Livorno turned this Baghdadi-Lurianic synthesis into the standard text, shipping siddurim across the Mediterranean and the Indian Ocean trade routes, so that a worshipper in Calcutta, Cairo or Casablanca came to hold substantially the same book, above local melodies and pronunciations that remained gloriously unstandardised.