Among these builders were, in England: William Wotton, who flourished in 1487, Chamberlyn (1509), Duddyington (1519), Perrot (1526) and White (1531); in Germany: Compenius, Schnitzker, Hildebrandt, Schmid, André, Kranz, Lobsinger, and the Trampeli; in Italy: the Attengnati family, Lorenzo di Giacomo, Luca Blasi, Vincenzo Columbi. It may be said that during the sixteenth and seventeenth centuries the organ assumed a form whose essentials--plurality of keyboards (manuals) and wind-chests, arrangement of stop action and pedals--have remained unchanged during succeeding centuries. Interesting as an incident in the development of the increasing secular use of the instrument is its introduction (in the smaller form) in the orchestra of Peri’s _Euridice_ (1600), the first opera, in which _un regalo_ and _Duoi organi di legno_ (portatives with wooden pipes) were employed. IV During the seventeenth century many mechanical devices intended to secure rapidity, ease and precision in organ playing were invented or perfected. The custom of tuning the organ according to the ‘unequal temperament,’ which made practicable the use of only sixteen keys, persisted throughout this century, and did not die out on the Continent until the next. The wind-gauge, invented in 1675 by Chr. F. Förner, was important, as it made possible the proper regulation of the wind-power in the various wind-chests and in the registers above them. In general, this century as well as that following are notable because of the addition of many new flute and reed-tone stops, and a general enrichment of the tone-color of the instrument; as well as the first general application of a thoroughly modern idea, the union of several distinct organs, each having a keyboard of its own, into one single instrument, though more than one manual had been used before this. Early in the eighteenth century the ‘swell’ is invented to vary the loudness of the organ tone, by an English organ-builder named Jordans (1712); and during the course of the century the softest sounding manual in the majority of English organs (known as the ‘echo’) is changed into a swell. On the other hand the pedal is practically unknown in England until the nineteenth century. Father Smith, Thomas, René Harris and Avery were prominent English organ-builders of the eighteenth century, as well as Samuel Green, who invented the horizontal bellows in 1789. The Silbermanns were the great German builders of the time, and from 1714 to 1817 various members of this family built remarkably fine organs, renowned for their tone quality and constructive excellence, in a number of German cities. One of the finest of the Silbermann organs is that of the Freiberg minster, built by Gottfried, in 1714; another is that of the Catholic Royal Chapel in Dresden.