From time to time in this gallery, you may notice unusual Yamaha upright models like this piano. Models like this are high-performance versions of an existing model, like the U1 in this case. The most distinguishing feature of the “X” models like this piano is the radial back-posts found in the back of the piano (see picture slideshow above) which add about 70 lbs to the weight of the piano and improve tone projection, power, sustain and tuning stability. The presence of sound vents in the front panel further adds to the vivid tone of these models. If you play, we think you’ll know the minute you put your hands on the keyboard that you’re in the presence of a superior upright piano.