Abstract: An upright piano includes an internal space enclosed by a case including an upper front board disposed above a key bed and a lower front board disposed below the key bed, and a resonance tube in which a hollow region having an opening is formed and that is disposed in the internal space, in which the opening is disposed at the left end of the lower end of the upper front board or the upper end of the lower front board, or at the right end of the lower end of the upper front board or the upper end of the lower front board.

Abstract: An upright piano includes an internal space enclosed by a case including an upper front board disposed above a key bed and a lower front board disposed below the key bed, and a resonance tube in which a hollow region having an opening is formed and that is disposed in the internal space, in which the opening is disposed at the left end of the lower end of the upper front board or the upper end of the lower front board, or at the right end of the lower end of the upper front board or the upper end of the lower front board.

Abstract: Keys of a piano are depressed against the total weight of associated action units and hammers so that balance weight pieces are embedded in the front portion of each key; since the wood bar of the key is expandable and shrinkable due to the conditions of the environment, the weight pieces are liable to come loose; the balance weight piece is formed with ridges and valleys repeated at least 7 times at fine pitches equal to or less than 2 millimeters, and the maximum diameter of the ridges is slightly longer than an inner diameter of a hole formed in the wood bar; while the balance weight piece is being pressed into the hole, the ridges make the inner surface portion elastically deformed; when the balance weight piece reaches the target position, the inner surface portion penetrates into the valleys so that the balance weight piece is lodged therein.

Abstract: Keys of a piano are depressed against the total weight of associated action units and hammers so that balance weight pieces are embedded in the front portion of each key; since the wood bar of the key is expandable and shrinkable due to the conditions of the environment, the weight pieces are liable to come loose; the balance weight piece is formed with ridges and valleys repeated at least 7 times at fine pitches equal to or less than 2 millimeters, and the maximum diameter of the ridges is slightly longer than an inner diameter of a hole formed in the wood bar; while the balance weight piece is being pressed into the hole, the ridges make the inner surface portion elastically deformed; when the balance weight piece reaches the target position, the inner surface portion penetrates into the valleys so that the balance weight piece is lodged therein.

Abstract: Keys of an acoustic piano require balancers for cancellation of a part of self weight of the action units/hammers; however, the balancers are liable to be dropped off due to the aged deterioration of the wooden bars; in order to keep the balancers stable in the keys against the aged deterioration, the balancer is plastically deformed so as to bite into the wooden bar, the balancer, which is formed with thorns, is rotated so as to make the thorns bite into the wooden bar, the balancer is shaped into a configuration different from the holes so as to exert resilient force on the inner surface in a direction in parallel to the grain of wood, or the balancer is inserted into a constricted hole so as to strongly exert the resilient force on the inner surface, thereby being prevented from the dropping off from the keys.

Abstract: Keys of an acoustic piano require balancers for cancellation of a part of self weight of the action units/hammers; however, the balancers are liable to be dropped off due to the aged deterioration of the wooden bars; in order to keep the balancers stable in the keys against the aged deterioration, the balancer is plastically deformed so as to bite into the wooden bar, the balancer, which is formed with thorns, is rotated so as to make the thorns bite into the wooden bar, the balancer is shaped into a configuration different from the holes so as to exert resilient force on the inner surface in a direction in parallel to the grain of wood, or the balancer is inserted into a constricted hole so as to strongly exert the resilient force on the inner surface, thereby being prevented from the dropping off from the keys.

Abstract: Keys of an acoustic piano require balancers for cancellation of a part of self weight of the action units/hammers; however, the balancers are liable to be dropped off due to the aged deterioration of the wooden bars; in order to keep the balancers stable in the keys against the aged deterioration, the balancer is plastically deformed so as to bite into the wooden bar, the balancer, which is formed with thorns, is rotated so as to make the thorns bite into the wooden bar, the balancer is shaped into a configuration different from the holes so as to exert resilient force on the inner surface in a direction in parallel to the grain of wood, or the balancer is inserted into a constricted hole so as to strongly exert the resilient force on the inner surface, thereby being prevented from the dropping off from the keys.

Abstract: Keys of a piano are depressed against the total weight of associated action units and hammers so that balance weight pieces are embedded in the front portion of each key; since the wood bar of the key is expandable and shrinkable due to the conditions of the environment, the weight pieces are liable to come loose; the balance weight piece is formed with ridges and valleys repeated at least 7 times at fine pitches equal to or less than 2 millimeters, and the maximum diameter of the ridges is slightly longer than an inner diameter of a hole formed in the wood bar; while the balance weight piece is being pressed into the hole, the ridges make the inner surface portion elastically deformed; when the balance weight piece reaches the target position, the inner surface portion penetrates into the valleys so that the balance weight piece is lodged therein.

Abstract: Keys of an acoustic piano require balancers for cancellation of a part of self weight of the action units/hammers; however, the balancers are liable to be dropped off due to the aged deterioration of the wooden bars; in order to keep the balancers stable in the keys against the aged deterioration, the balancer is plastically deformed so as to bite into the wooden bar, the balancer, which is formed with thorns, is rotated so as to make the thorns bite into the wooden bar, the balancer is shaped into a configuration different from the holes so as to exert resilient force on the inner surface in a direction in parallel to the grain of wood, or the balancer is inserted into a constricted hole so as to strongly exert the resilient force on the inner surface, thereby being prevented from the dropping off from the keys.