A Dictionary of Music and Musicians/Tremulant
TREMULANT. A contrivance in an organ producing the same effect as tremolando in singing. Its action practically amounts to this:—the air before reaching the pipes is admitted into a box containing a pallet to the end of which is attached a thin arm of metal with a weight on the end of it; when the air on its admission raises the pallet the metal arm begins to swing up and down, thus producing alternately an increase and diminution of wind-pressure. Its use is generally limited to such stops as the Vox humana and a few other stops chiefly of the reed family. The tremulant is happily much less in vogue in this country than on the continent, where its abuse is simply offensive. It is difficult to conceive how good taste can tolerate these rhythmical pulsations of a purely mechanical pathos.
[ J. S. ]