By John Thompson
Many of us who restring or carry out concert service will be accustomed to levelling strings. This process involves pulling or massaging the string up or down so that the note/unison is level and on the same plane as the action rail/keybed. This is important as if they are not level, you can get voicing issues and poor damping.
The brass bubble
This process is always done after restringing or when voicing. You want the hammer to hit all the strings of the unison at the same time. Once the strings are level, you mate the hammers to the strings. One tool for this work is the brass bubble. A brass weight with a liquid bubble gauge which sits on the strings in the unison and you can see if the strings are on the same plane by the bubble and by plucking the strings, you can hear if they are level. It’s a fiddly job but in theory, you don’t need to do it that often.
The problem with the brass bubble
However, I don’t like the brass bubble for a few reasons. Firstly you have to either remember what the bubble should look like according to the keybed etc. or shim the piano to make it level. You then need to adjust the strings and constantly keep the bubble correct. It’s also difficult near the breaks where the cast bracings can get in the way. Due to its size, plucking the strings can make it unstable so defining which strings needs adjusting can be difficult.
The damper head also gets in the way as the best point to use is at the strike point of the hammer. Some technicians learn to use it well, but I have found a better tool for the job.
The better tool
Enter TPR Tools. This works from underneath thes being able to place the tool at the strike point and avoiding the cast struts at the breaks. Using this on the keybed also means you are using the same plane as the action, and hammers, so no need for a bubble. It uses an aluminium strip, 3 are available in different lengths and has a light spring giving the aluminium strip some bounce but not enough to push the strings up.
Placed under the strings, you pluck the strings and listen. The tool also works as a keybed to string height gauge, allowing you to mark 10 positions using a fine felt tip.
A tightening wheel allows you to lock the aluminium at the height so you can retrieve the tool and keep it at the right height. If the keybed is not completely solid and flat, it has open sections meaning the tool cannot be kept flat under the strike point, you will need a flat wood to provide a platform. The price for this tool may seem high, but like all specialist tools, they are made in small numbers. You could also make one if you have the time and machines to do it. However, I simply don’t have the time, so for me it was worth the expense to save me time and have less frustration while working on a piano. I have a number of tools by TPR, the regulation rack is probably the best out there. I will review this for you another time.