Ostrolenk, Faber, Gerb & Soffen
Piano construction for enriched stereophonic tonal radiation
 At least one board defining the front side of the resonant cavity of a piano is provided with at least a pair of outwardly diverging vertical slits arranged an appreciable distance away from each other and on opposite sides of the center of the piano for smooth radiation of tonal atmospheric vibrations generated in the cavity by striking of strings to the atmospheric space in front of the piano, thereby providing ideal stereophonic acoustic effect to the player or listeners and avoiding any biased cavity resonance and mixing of undesirable noises. A selectively openable construction of the slit enables free selection of the tonal radiation in accordance with the requirements of the performance. 
Nippon Gakki Seizo Kabushiki Kaisha
G
G10C
inventional
Hideo
Yamashita