226 S. A. Hageman — A Just Intonation Piano. 



defects and intricacies, — and last but not least, make light 

 demands upon the purse. 



The ordinary piano has, therefore, been taken as a founda- 

 tion for the new, and without taking from the player his 

 familiar instrument, he is enabled to instantly substitute, for 

 its tempered harmonies, mathematically just intonation in 

 twelve keys based on the twelve tempered chromatic intervals 

 of the octave. 



The changes from one to the other of these twelve justly 

 intoned keys (each having its own complete chromatic scale), 

 or back to temper again, is under the instantaneous control of 

 the left foot, so that the right is left free to operate the damp-' 

 ers as usual. 



The absolute uniformity of the tempered scale with its 

 twelve equal intervals makes it admirably suitable as a basis 

 for the necessary corrections, and its adoption as such essen- 

 tially simplified the problem. 



The modification of the evenly tempered intervals, to make 

 them conform to those of true intonation, is effected by a line 

 of small metallic movable bridges. 



Each unison has a separate bridge which is capable of being 

 moved toward the center of the string, thus shortening the 

 vibrating portion and raising the pitch, or, it may, by a con- 

 trary motion, cause a depression of the pitch. When the 

 instrument stands in temper the bridges will occupy the usual 

 line of the agraffe, which is set back far enough to make room 

 for them. Mechanism for the proper control of these bridges 

 is placed on the top of the wrest plank and at the back of the 

 piano and is actuated by intonation pedals which pass beneath, 

 at the left of the center. When an intonation pedal is pressed, 

 every bridge is instantly set, so as to give the mathematical 

 cord length for its tone in that key, in which position it 

 remains until reset by the same means. 



In the instrument as at first constructed, there were thirteen 

 pedals, representing the twelve just keys and the even temper. 

 A much simpler and better arrangement has been since adopted. 



Description of Parts. — Fig. 1 is a vertical section of part of a 

 piano adjacent to one of the movable bridges, showing side eleva- 

 tion of string, movable bridge and parts related. 



Fig. 2 is also a vertical section taken on the line X, at right 

 angles to the section of fig. I, and is drawn to a larger scale. 



The string, or group of strings forming one unison, is shown at 

 a, passes over the movable bridge b and the agraffe g to the wrest 

 pin/. 



The extreme phases of vibration of the string are shown by 

 the dotted lines a' a". The rod e is attached to the bridge b t 



