Bedding the Steinway Keyframe
Steinway designed the frame on which the keys are located, called the keyframe, to be adjustable for wear and tear, and for the movement of its components, which inevitably occurs due to warping and shrinkage.
No other maker in the late-1800s had this feature, but now almost all have adopted it, which is simple but takes a lot of practise to set up correctly.
No proper regulating of a grand piano with adjustable keyframe is complete unless this work is undertaken.
The system is necessary because the whole keyframe shifts from left to right on depression of the soft (una corda) pedal, so it therefore needs to glide, but remain in contact with the keybed correctly at all times. Uprights don’t need this, because their keyframes are fixed, and the left pedal merely moves the hammers closer to the strings - which is why an upright’s left pedal is called a soft pedal rather than an una corda, as it doesn’t shift the action and keys to miss one of the strings (unisons), in the groups of two or three strings that make one note, on all pianos.
The adjustment firstly involves the scrupulous cleaning and gentle sanding of keyframe and keybed, taking care not to sand the front and rear half inches of these or the hardwood buttons in the keybed.
The pictures show the key-blocks, the pins on which they bear, the domes, and their stems, the adjusters; also, the hardwood inserts in the keybed (that part of a grand piano on which the keyframe is located, and on which the domes bear).
With the action and keys properly located in the keybed, and the shift on the pedal correctly adjusted and lubricated, and the keyblocks properly screwed down, the keyframe is then bedded at the front, so it doesn’t slap - this is done by tapping it with the fingertips along its entire length, and if it knocks in a hollow way, remedial action, is called for, such as sanding, or careful adjustment of the keyblocks’ bearing on the keyframe’s locating pins, with gummed paper. Then, the painstaking process of adjusting the domes is undertaken, the first dome being adjusted for pressure on its hardwood bearing point in the keybed. This is done by gripping the stem between thumb and forefinger of one hand, while tapping the keys just in front of the middle bushing chasing with the finger tips of the other.
When lifted hard, a hollow knocking should be clearly heard; this is achieved by raising or lowering the dome by means of a short piano tuning crank being placed on its stem, and turning clockwise to increase pressure, and vice-versa. Naturally, adjusting one dome correctly affects all the others, always - so it’s a process of constant adjustment and back-tracking, which can easily take an hour or more.
When done, the key-frame shifts easily, bearing as it does only on its six domes and the front and rear half inch of it, and the keyblock-locating pins. As one is, in effect, raising and lowering the middle keyframe rail, thus influencing key-height and depth of touch directly, no proper regulating of a grand piano with this system is complete unless this work is undertaken.