sition of large organs—many of them containing over six thousand—so as to get them under the command of the narrow compass of the manuals, reveal wonderful ingenuity, quite apart from the musical effects capable of being represented through the instrumentality of that noble art medium. Formerly the pipes were attached to one key-board. Then came the disposition of the pipes with two manuals and two cases. These were consequently termed double organs. A modern instrument is found in many instances to contain five separate organs within its case, but being all under the control of the organist, they are spoken of compositely as one instrument, though particularized in giving a description by their names—grand, swell, solo, choir, and pedal. 
Fig. 23.—Popular Style of Modern Parlor Organ. Emphasis has been laid on these points in order to give readers a clear idea of the terms used elsewhere in speaking of the instrument.
The aim of the organ-builder has been to increase the variety and extent of the sounds, so as to render them available for art purposes through the instrumentality of the key-board and pedal system. And in the order of things, when the number of pipes was added to from time to time to give increased compass, it became necessary to originate improvements in the wind collecting and distributing departments. These are, first of all, the bellows, then the wind-chest, wind-trunk, and sound-board grooves. Meantime it is seen that the perfection of this department, so to speak, was such that it permitted the builder to apply air to the action mechanism according to the laws of pneumatics, with obvious advantage. In the early centuries the instrument was blown with a rude bellows by hand; then came the pedal bellows described by Prætorius, in 1620, which he found in the ancient organ in the church of St. Ægidien, in Brunswick. This system re-
