Some Yamaha upright models use X-shaped back posts for
 their soundboard. This X-back post is in integral structure,
 strengthening 2.5 times stronger against twists caused
 by string tensions. This leads to stabilizing the soundboard
 and the sound itself. It is said that Yamaha studied
 this structure from Grotrian Piano Company,
 who called it the "Singing board."

 Yamaha stopped manufacturing pianos with X-back posts today,
 largely because of their high manufacturing costs.
 Thus, the pianos with X-back posts can be purchased only as
 "used pianos." Pianos with this structure are scarce,
 with its popularity recently rising in Japan as well as overseas.
 As they are Yamaha's premium models, they are not in affordable price ranges.
 However, certainly it would be eye-catching product with extra
 values & characteristics for your store.