Chapter Stone Soup to Stops of S by Brewer's Phrase & Fable

agrees with the normal pitch of the digital struck, or some octave of it.
   The mutation stops produce a tone that is neither the normal pitch nor yet an octave of the digital struck.
   The mixture stop needs no explanation.
   Among varieties of organ-stops may be mentioned the complete stop, which has one pipe or reed to a note. The compound stop, which has more than one pipe or reed to a note. The flue stop, composed of flue-pipes. The incomplete (or imperfect) stop, which has less than the full number of pipes. The manual stop, corresponding to the manual keyboard. The open stop, which has the pipes open at the upper end. The pedal stop, as distinguished from the “manual” stop. The solo stop, the string stop, etc.