Aaron ben Asher אהרן בן אשר

The consonantal text of the Tanakh had been transmitted for centuries, but the vocalisation, the accents and the marginal notes — the masorah — took shape in Tiberias in the ninth and tenth centuries. Several families worked on it; the system of ben Asher prevailed.

The Aleppo Codex is the best-known manuscript of that tradition. The consonants were written by Shlomo ben Buya'a around 920, and the vocalisation, accents and masorah were added by Aaron ben Asher. Maimonides says outright in the Mishneh Torah that he relied on this manuscript in determining what a valid Torah scroll must be — Hilchot Sefer Torah 8:4; tradition adds that he personally checked a scroll against it in Fustat.

The ben Naftali family worked in parallel, and the differences between the two systems touched hundreds of places — almost always small ones: an accent, a vowel, a verse division. The ben Asher tradition won out, and printed editions of the Tanakh descend from it.

Whether he himself was a Karaite is an open question. Many scholars incline to the view that the ben Asher family were Karaites, but the evidence is judged insufficient and there is no consensus. It is said here exactly that way, and not decided in either direction.