Hope-Jones has also recently invented a means of controlling the swell shutters from the manual keys to a sufficient extent to produce certain sforzando effects.
When this contrivance is brought into use upon any manual and when no keys upon that manual are being played, the swell shutters assume a position slightly more open than normal in relation to the position of the swell pedal. Directly any key upon the manual in question is depressed, the swell shutters again resume their normal position in relation to the swell pedal. This results in a certain emphasis or attack at the commencement of each phrase or note that is akin to the effect obtained from many of the instruments of the orchestra.
These contrivances are applicable only to such organs as have the balanced swell pedal.
The invention of the Swell is generally attributed to Abraham Jordan. He exhibited what was known as the nag's head Swell in St. Magnus' Church, London, England, in the year 1731.
The "nag's head" Swell, with its great sliding shutter, rapidly gave place to the "Venetian" Swell shades, used almost universally to this day. At the beginning of the period under consideration Swell boxes were almost invariably made of thin boards and their effect upon the strength of the tone was small. Willis was one of the first to realize the artistic possibilities of the Swell organ and in almost all his organs we find thick wooden boxes and carefully fitted shutters, and often an inner swell box containing the delicate reeds, such as the Vox Humana and Oboe.
Many of the leading organ builders now employ this thicker construction, and it is no uncommon thing to find Swell boxes measuring three inches in thickness and "deadened" with sawdust or shavings between the layers of wood of which they are formed.
A few organs of Hutchings and other makers are provided with a double set of shutters, so that sound waves escaping through the first set are largely arrested by the second. The _crescendo_ and _diminuendo_ are thus somewhat improved.
By the adoption of scientific principles Hope-Jones has multiplied the efficiency of Swell boxes tenfold. He points out that wood, hitherto used in their construction, is one of the best known conductors of sound and should, therefore, not be employed. The effects produced by his brick, stone and cement boxes (Worcester Cathedral, England; McEwan Hall, Edinburgh, Scotland, Ocean Grove, New Jersey, etc.) mark the dawn of a new era in Swell-box construction and effect. It is now possible to produce by means of scientific Swell boxes an increase or diminution of tone amounting to many hundred per cent.
