Bless, O Lord, us thy servants,
who minister in thy temple.
Grant that what we sing with our lips,
we may believe in our hearts,
and what we believe in our hearts,
we may show forth in our lives.
Through Jesus Christ our Lord.
The Chorister’s Prayer seems to have first appeared in The Choirboy’s Pocket Book, published by the School of English Church Music (the former name of the RSCM) in 1934. Despite being so well known, the prayer is not given an author in this source (some say it was the RSCM’s founder, Sir Sydney Nicholson, while others link it to Cosmo Gordon Lang, who became Archbishop of Canterbury in 1929).
The English version of this Prayer appears to be very close to the Latin in the Pontificale Romanum of 1595–96 in the form for admitting a Psalmista or Cantor:
Vide, ut, quod ore cantas, corde credas, et quod core credis,
It may be even older (perhaps 13th or 14th century).