Key Weighting

This post is intended to suggest a possibly lesser known “aid” for tuning the entire piano. Not included in this discussion are such basics as temperament, tuning checks to use, methods of tuning and electronic instruments if one is used. This post will focus on “fine tuning” a piano that is already at the A440 pitch level and in fairly good, even tensions in all sections.

While tuning certain pianos, particularly the older uprights, all of us have encountered certain strings, usually the longer tenor ones, that suddenly start to ring or sound while tuning due to sympathetic vibration. It was exactly this situation that prompted further study and the exploration of these “open” strings as an aid in aural tuning. It was further noted that the more in phase the octave being tuned, the louder and clearer the sing-through sound created by sympathetic vibration.

This article assumes that the reader also understands at least some of the physical characteristics of vibrating piano strings, their modes, partials and inharmonicities.

The principal of weighting keys is to deliberately raise the damper, freeing the string to sound sympathetically as related intervals are being tuned. The louder and clearer the sound of the weighted-open note, the better in tune the interval being tuned. This is the main principle of the system. Primary intervals in key-weight tuning are the octave, fifth, octave fifth and the double octave fifth. We hope to stimulate enough reader interest for many to actually experiment with the use of key-weighted open sounding strings in tuning.

One very discriminate college piano teacher once remarked, “I am more interested in the fifth being in tune than the simple octave.” Of course what she was favouring was really the 6:3 octave tuning instead of using only the fundamentals in tuning the octave 2:1. A good example of “fifth” tuning is in the matching of the fundamental and the fifth in bass tuning which is fairly standard and well known by most tuners.

In regard to the type of key weight used, anything of size and shape, heavy enough to hold any key fully depressed to open the dampers, is fine. It must also conform in size and shape to hold only one key down at a time, including the sharps, without falling off easily. It is also suggested that the weight be felt covered to eliminate the possibility of scratching any keytops.

BASS TUNING USING KEY WEIGHTS

After completing a fine-tuned temperament, extend accurately the first few notes up to the first B natural above (B4)*. The reason for tuning up these few notes is to have in tune the first fifths to weight keys open before starting the bass tuning. For example, the first note of the bass section below temperament is E3. Now place the weight on ...

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https://www.professionalpianotunerlondon.co.uk/post/key-weighting