The smaller a piano, the more attention to detail and precision is needed.
Many upright pianos and even some grand pianos use only the cast iron plate as a termination point for the speaking length of a piano wire. That particular metal is very hard and brittle which does well enough for enhancing the bright timbre of a note but can be unforgiving when you’re trying to achieve a deep, dark tone.
Lower pitches are achieved with longer and heavier wire – there’s so much weight and therefore more energy to generate the volume required that balance is easier to achieve with a softer metal. The softer metal absorbs some of the brightness and the bass bridge should provide enough motion for the lower vibrations to speak beautifully. On the Hailun upright, the termination point near the tuning pins has a uniform cut-off because the angle of the string to that termination point is set within the agraffe and not by how far the tuning pins are driven into the pin-block.
As you move to the tenor section the strings are linked bearing down on the bridge where the soundboard is the widest across the grain. This allows for more energy to be evenly distributed through the soundboard (acoustic membrane). Here we achieve uniform down-bearing with a capo bar – the same is true in the treble. On most pianos the cast iron forms the termination point, but on the Hailun the tenor section has a brass rail which can be replaced if ever needed. The fact that the rail is brass means that it is a much softer termination point for the tenor and it also is a larger diameter than the treble, this helps to support those singing tones we love so much in the mid-range.
The treble section has a similar design to the tenor with one important change: The termination rail is made of stainless steel and is a smaller diameter. This gives the higher notes more precision and support for clear tone projection. The shorter the strings get, the more precise all our measurements need to be- the length, weight, and hammer strike-point can make or break an entire piano in the high treble.