Reprinted with permission from Louis Jacobs, The Jewish Religion: A Companion, published by Oxford University Press.
"Cantor" [(Hebrew hazan, plural hazanim; but see below) is the term used in English for] the prayer leader in the synagogue. In rabbinic times [first century BCE to the end of the Talmudic period in the sixth century], many people were unfamiliar with the prayers, and so in public worship a man well versed in the liturgy would recite the prayers aloud with the congregation responding to his benedictions with "Amen," this being considered as if they themselves had offered the prayers. Even after the wide dissemination of the Prayer Book, the institution of the prayer leader was continued, so that the prayers were then recited by both the congregation and the reader.
Names and terms
In the Mishnah, the leader is called "one who descends before the chest." (The Ark [in which Torah scrolls are kept today] in the ancient synagogue was not built into the wall of the synagogue but consisted of a portable chest containing the Sefer Torah.) Other terms found in the sources are sheliah tzibbur ("messenger of the congregation"), abbreviated to shatz (hence the Jewish surname Schatz) and hazan (originally meaning "overseer"), the name most frequently used. [The Jewish surname Chazan, in various spellings, is derived from this term.]
The hazan was not a special functionary. Any member of the congregation was qualified to lead the congregation in prayer. But in the course of time, specially qualified persons were favored to act as hazanim. The term "cantor," adopted by Western Jews in modern times, is not found in the traditional sources and is used chiefly for a man [for a woman, hazzanit] with special musical qualifications who sings accompanied by a choir. The modern cantor is a special salaried official. In this [article] the term "cantor" is used to denote every variety of prayer leader.
Who Is the Ideal Cantor?
A section in the [16th century code of Jewish law called] Shulhan Arukh (Orah Hayyim, 53) is devoted to the qualities ideally required for a hazan. He should be without sin (comparatively speaking, of course, since no one is free from sin); he should be free of rumors that he had a bad reputation in his youth; he should be a modest man and acceptable to the people for whom he deputizes; and he should have a pleasant voice. If such a paragon is not to be found, this source adds, somewhat laconically, that the man chosen should be the most pious and learned in the congregation. (For this reason it is customary in Hasidism for the rebbe, the Hasidic master, to act as prayer leader.) The hazan should be at least 13 years old and should be male. (In many non-Orthodox congregations women cantors are now appointed.) Ideally a hazan should have a full beard, but this was later interpreted to mean that he should be of an age when the beard is fully grown, that is, he should be a mature person, who is then acceptable even if he does not actually sport a beard.