Abstract: An amplifier circuit for automatically altering in a controlled way the reproduced tones of an electronic piano comprises a main signal path for the fundamental tones and an overtone path including a plurality of tone altering electronic networks and field effect transistor amplifiers combining the networks. The circuit includes separate controls for manual adjustment of normal level gain, bass boost, overtone, output volume and gate control threshold. A mixer recombines the main path and the overtone path. A gate circuit may be provided to disable the overtone path when no signal is present in the main path over a predetermined minimum threshold. The entire device is constructed for mounting over the keyboard of the piano, with a panel for the controls which renders them readily accessible for regulation by the musician to obtain the desired improvement and alteration of the tones put out by the piano.

Abstract: In the herein illustrated embodiment the harp or tone generator assembly of the piano is supported pivotally at one end so as to pivot in a substantially horizontal plane on its support, and a mechanism manipulated by the player shifts the movable end of the harp thereby to shift the position of the tone generators in the harp relatively to the percussion hammers, so that while the keys of the piano are depressed for playing, the player can selectively change the tone at will; an amplifying circuit compensates for the loss of volume due to the shifting and to the resultant change of the striking line.