Select the right type of Stephen Paulello wire, whatever the piano


To choose the type or types of strings suitable for each note of a piano, you should note down the scaling and enter every dimension in the Excel calculation sheet especially conceived for this purpose: the Typogram.

It is free of charge, can be downloaded and opened with an Excel program or equivalent.

Positive effects of stress rate on a string

According to the stress intensity, the steel does not react in the same way :

  • In the medium and low-medium, the metal is most of the time not enough stressed. Standard steel is in fact too resistant compared to the tensile strength to which it is subjected (the more so if the pitch is low). When not "stimulated" enough, the material has considerable internal damping which absorbs a part of its potential. The sound of an under-stressed string is dull, blurred and hollow.
  • In the high trebles, the problem is the opposite: the material is highly stressed, sometimes so much so that it is too close from its breaking load. While the wire gets tightened, distortions and alterations occur  within the metal, so that, if it is not resistant enough, false beats can appear and the string can become brittle. Moreover, the sound of an over-stressed string  is thin and has little power.


Changing the type of wire does not affect the tension of the string, it only affects the stress rate of the metal.  
The stress rate of a string depends mainly on its vibrating length, the frequency at which it is tuned  and the breaking load of the material.

Consult the technical files to learn more

Make a note of the scaling

Measuring and noting down the dimensions  is an important step necessitating concentration and precision. It is easy to forget a note or to place oneself on a note on the agrafe side and on the neighboring note on the bridge pin side. It is strongly advised that two people undertake this work together. If you have a portable computer, keep it close to you so that you can enter the elements into the program as soon as you have measured them.

Measuring vibration lengths :
You will obtain the most accurate measures by using steel rules of different sizes. Take the middle of the agrafe or the middle of the capo d’astre as departure point, and the middle of the front bridge pin (situated towards the vibrating part of the string) as the arrival point.

Measuring diameters :
If there is no number on the frame or on the bridge, and the model of piano is unknown, use a micrometer to measure the diameter of the existing strings, or ask for a calculation of the scaling.

How to fill the Typogram

  1. Following the above instructions, make a plan of the instrument’s scaling (in millimeters)
  1. Fill out the blue columns of the Typogram with the figures you have measured and noted down
    - For the diameter of bass strings, enter core wire diameter and total diameter
    - For the diameters of plain strings, enter twice the same value
  1. Indicate the diapason to which the piano will be tuned
  1. In the “TYPE” column, juggle between XM, M, 0(zero), 1 or 2 and observe, in the next column, the reactions of the stress rate.
  • In the bass, the ideal stress rate is around 50% at the break. It can go as high as 70% for the last unichord but it is preferable not to exceed 60%
    Try to equalize the stress rate at the break from bichords to unichords: for example, choose type M for the last unichord and type 0 for the first bichord.
    Then, if the last bichords are over-stressed, use type XM.
  • For plain strings, the stress rate should be around 50% in the medium bass. The medium should develop from 50% to 60% at the level of  A3. From A3 to the highest treble, the stress should increased regularly and can reach 80% for the last notes.
  1. To make your order, write to : wire@stephenpaulello.com