Abstract: It is important for an upright piano to keep a keyboard on a key bed horizontal, and the key bed is supported by a frame through coupling units, wherein each of the coupling units has a wedged member interposed between a projection of the frame and a bracket of the coupling unit or between the bracket and the key bed for regulating the horizontality of the keyboard.

Abstract: A circuit for conference telephony using a conventional system for transmission of voice data and having no use for the conventional hybrid station is materialized by this invention using at least two buffer memory circuits provided for each of the frames and adapted to be switched to each other one for input and the other for output, enabling one of the buffer memory circuits to memorize voice data transmitted thereto and, in the meantime, permitting the voice data of the preceding frame memorized in the other buffer memory circuit to be read out, converting the voice data so read out to be converted into analog signals, and synthesizing the analog signals one another.

Abstract: In construction of a keyboard unit accommodable upright piano, a vertically turnable keyboard is held by a holder unit so that the keyboard unit can be stably held in a horizontal position at one state of the holder unit and easily be accommodated in the main casing at the other state of the holder unit.

Abstract: In the construction of a housing for upright pianos, as a substitute for the conventional hard, thick and heavy wooden boards associated with back posts vulnerable to circumstantial changes, soft, thin and light wooden boards are attached to a metallic skelton of a substantially rectangular construction suited for supporting a keyboard assembly. Weight of the housing is greatly reduced without impairing strength and no use of back posts makes the housing well durable against changes in environmental factors.