To arrange, by means of a mechanism called a coupler, that the pedal org. can have one or more of the manuals connected with it so that the effect of its stops is reinforced. Two manuals can be connected in the same way (e.g. the swell may be joined with the great). There are ‘super‐octave’ and ‘sub‐octave’ couplers which duplicate the notes played, an octave higher or lower (on the same stop). Couplers are 4′, 8′, and 16′.