A Dictionary of Music and Musicians/Register (organ)

REGISTER, of an organ. Literally, a set of pipes as recorded or described by the name written on the draw-stop; hence, in general, an organ-stop. The word 'register' is however not quite synonymous with 'stop,' for we do not say 'pull out, or put in, a register,' but, 'a stop,' although we can say indifferently 'a large number of registers' or 'of stops.' The word is also used as a verb; for example, the expression 'skill in registering' or 'registration' means skill in selecting various combinations of stops for use. The word 'stop' is however never used as a verb, in this sense.

[ J. S. ]