Master of the Children is a title awarded to an adult musician who is put in charge of the musical training, and in some cases the general education (which sometimes gets offered as a priceless perk to recruit the best singers) of choir boy (or since the late 20th century in a growing number of choirs boys and girls), as was common in major church choirs, often attached to a cathedral

Cathedral

A cathedral is a Christian church that contains the seat of a bishop...

, monastery

Monastery

Monastery denotes the building, or complex of buildings, that houses a room reserved for prayer as well as the domestic quarters and workplace of monastics, whether monks or nuns, and whether living in community or alone .Monasteries may vary greatly in size – a small dwelling accommodating only...

, collegiate church

Collegiate church

In Christianity, a collegiate church is a church where the daily office of worship is maintained by a college of canons; a non-monastic, or "secular" community of clergy, organised as a self-governing corporate body, which may be presided over by a dean or provost...

 or court chapel, such as the musically particularly significant English Chapel royal

Chapel Royal

A Chapel Royal is a body of priests and singers who serve the spiritual needs of their sovereign wherever they are called upon to do so.-Austria:...

, to train the young recruits (not just as future adult singers but at least as much because their treble

Boy soprano

A boy soprano is a young male singer with an unchanged voice in the soprano range. Although a treble, or choirboy, may also be considered to be a boy soprano, the more colloquial term boy soprano is generally only used for boys who sing, perform, or record as soloists, and who may not necessarily...

-boy soprano- voice was considered angelic, hence liturgically ideal).