I ran across these three beautiful prayers, for use by choir members:
The Chorister's Meditation when vested in the Surplice
Cleanse me, O LORD, and keep me undefiled, that I
may be numbered among those blessed children, who
having washed their robes, and made them white in the
Blood of the LAMB, stand before Thy throne, and serve
Thee day and night in Thy temple. Amen.
The Chorister's Prayer before Divine Service
O LORD, open Thou my lips, that my mouth may
show forth Thy praise, and purify my heart that I may
worthily magnify Thy glorious Name; through JESUS
CHRIST our LORD. Amen.
The Chorister's Prayer after Divine Service
Grant, O LORD, that what I have sung with my
mouth, I may believe in my heart; and what I believe in my heart I may steadfastly fulfil; through JESUS CHRIST our LORD.
