Diagnosing the General Condition of Your Piano
William Leland, D.M.A., R.P.T.
s the piano a string instrument or a percussion instrument? Actually, it is both. It’s a string instrument because its sound is produced by vibrating strings, and it’s a percussion instrument because the vibration is set in motion by striking them, rather than by bowing or plucking them. It seems simple enough: you push down one end of a long wooden lever, and a felt-covered mallet at the other end swings up (or forward) and hits the corresponding string. So why do pianos have to be so big, heavy and complicated? What can a piano owner do to understand the condition of his piano and diagnose problems?
These hints apply only to basic items that can be determined without any major disassembly of your piano; we do not recommend removing the action or any other parts of the piano yourself.
Even a small spinet weighs as much as a washing machine, and a large grand can be well over half a ton; all of them have a bewilderingly complicated mechanism inside. It’s part of the price we pay for preferring an acoustical musical instrument, one that does not rely on electronics to generate a sound. As the piano evolved through the 18th and 19th centuries, composers and performers demanded more and more power, brilliance and flexibility, so the piano grew essentially in three ways: its range expanded in both directions, from four-plus octaves to the modern seven octaves and a minor third; the number of strings increased, to three per note from the tenor section on up and one or two in the bass; and, most significantly, its power was enormously increased, primarily by raising the string tension. And whereas the tension in the early piano could be supported by a wooden case, the modern instrument must accommodate a combined string tension of some twenty tons. It is for this reason that it has to have a large cast iron frame inside, and that is where most of the weight comes from.
Accompanying this growth was the development of the action mechanism, which had to be designed to do five things:
We can appreciate the genius of the piano’s inventor, Bartolomeo Cristofori, by the fact that he solved all five of these problems at one stroke. A great number of different action mechanisms have been tried during the piano’s history, but, even though there have been many refinements to it, our modern grand is still based on Cristofori’s basic design.
1. Unisons: play single notes in different registers and listen for beats. 'Beat' is the term for the wavering "wah-wah-wah" sound caused by interference between the pitches of two or more strings that are not in tune. The faster the beat, the more out of tune they are.
2. Octaves: play octaves in various registers and listen for beats, but it may be difficult to distinguish between beats coming from the octaves and those from the two individual notes. It's helpful to pinch off the outer strings of each three-string note so that you're hearing only the middle string of each (you may need two people here). Check pairs of notes separated by double and triple octaves as well.
3. Other Intervals: this is a bit more complicated, because certain beats should be present in all the other intervals of a well-tuned piano. The reason for this is that our tempered scale, in which the octave is divided into twelve equal semitones, is a necessary compromise which deviates from the pure mathematical relationships of an acoustically perfect scale. It permits acceptable combinations in all keys without having to have some 86 notes in each octave, but it also means that all intervals other than unisons and octaves are actually out of tune: fifths only slightly, fourths a bit more, and thirds, sixths, seconds and sevenths quite a lot. The best way to check these is to compare similar intervals by moving chromatically within a short range, preferably in the middle register. Major thirds, for example, make a pleasant shimmering sound, and with practice it becomes fairly easy to compare the sound of adjacent thirds and note sudden changes in their general quality; the speed of the beat should increase very smoothly and gradually as you go up the scale by half-steps. Perfect fifths are easy: since the beat of a fifth is very slow, any fifth that sounds really sour is out of tune.
1. Look at the striking surfaces of the hammers. (In a grand you'll need to look down between the strings, so depress some keys to raise the hammers closer, and use a good light.) Any hammer of even a fairly new piano may have three faint marks on it (two or one in the bass) from striking the strings, but you're looking for definite grooves. If they are deep and elongated, and the crown of the hammer is visibly flattened, then hammer reshaping or even replacement may be in order. Note, too, if the marks are centered; if they are not, the hammer is out of line. (Often one even sees a tenor or bass hammer that has had a piece sliced off one edge by the heavy copper-wound lower strings.)
2. Check the strings and their tuning pins for rust or heavy accumulation of dark residue.
3. Look carefully at the treble and bass bridges (the long strip of wood over which the strings pass on their way from tuning pins to hitch pins). Note that each string is guided over the bridge by a pair of bridge pins: check for cracks around them.
4. Look at the soundboard, from both above and underneath (or behind, in a vertical). A crack or open seam may or may not be a major problem. If you see one, examine it from the back side at the points where the ribs cross it; if one edge of the crack is higher than the other and has become detached from the rib, the crack is probably serious.
The most serious problem that can occur with a soundboard is loss of crown. Crown is the slight upward 'bow' or curvature in the board that provides spring-like tension against the downward pressure of the strings, ensuring a tight connection through the bridges between strings and soundboard. Its presence can be detected by stretching a thread or string across the back side of the board, positioned between and parallel to the longest two ribs. When stretching the string tightly and pressing the two ends firmly against the two edges of the soundboard, you should detect a gap in the center between board and string. It won't be much--as little as an 8th of an inch or even less--but it's presence indicates that the soundboard has crown.
NOTE: The following hints apply only to basic items that can be determined without any major disassembly; we do not recommend removing the action or any other parts.
After folding back the front section, raise the lid all the way and prop it.
Remove the music rack. Most racks will simply slide off a track; a few must be slid forward enough to find the slot on each side, then lifted out.
If the fallboard (the panel behind the keys which serves as a keyboard cover) can be removed independently, it can be released either by pressing back against the spring clips at one or both ends, or by loosening a small screw at each end which holds it in a brass slot. This may be all you have to do.
If the fallboard is attached to the blocks at each end of the keyboard, then they and the key slip (long strip in front) will have to come off. If the key slip comes off independently you simply remove the screws underneath. Steinway key slips simply lift up out of several holes (be careful not to knock off any key covers in the process!); Asian pianos usually have a key slip that is held down by the blocks.
The blocks are each held by a large screw directly beneath the keybed; (be sure you find the right one--there are other screws down there which hold the case together.) Most Asian and some European grands have a wing nut instead, which can be removed by hand.
2. The front panel and music desk is held by a clip on each end, inside the top; the bottom edge may be held in place by a peg and hole arrangement, or, in old uprights, it may swing out to reading position when the fallboard is opened. Lift the entire section out and off.
3. The kickboard (panel above the pedals) can be removed by compressing the clip(s) at the top; the bottom edge will be in peg holes or a groove.
Squat or kneel so that your eye is level with the surface of the keys, and sight down the length of the keyboard from one end. The line of keys should be level; if there are noticeable dips, especially in the middle section, the key height is out of regulation.
Check the key dip; this is the distance the key surface travels from rest position to the bottom of the stroke; it should be 3/8" or a little more (some small spinets go much deeper to compensate for the very short keys). If the key level has sunk, the dip will be shallow. Compare some keys in the center with keys at the extreme ends that are not used much and may still be in better regulation.
In grands, check the hammer line: the surfaces of the hammers should make a straight line, but this can be deceptive: the hammer shanks (round sticks on which the hammers are mounted) must not be resting on the felt rail or pads beneath, but should be held in position by the action parts below them. . On verticals, this check is not necessary, since the hammer shanks rest on the soft pedal rail.
Check the striking distance. The hammer at rest should lie 1 3/4 to 1 7/8 inches from the strings.
Check the letoff or escapement. Depress a key all the way down, very slowly so that it doesn’t strike the string, and note when the hammer trips back. It should reach a point 1/16" to 1/8" from the string before escaping. Do this with a number of keys in different registers.
Check the damper pedal. If it has gotten too loose, there will be a noticeable gap in descent before the dampers begin to lift, and they may not even clear the strings entirely. If it's too tight, some dampers may be 'leaking', that is, allowing stray sounds to keep ringing because some dampers are not fully settled on their strings.
There are many other regulation settings, but these are the main ones which can be easily checked out with a good eye and a six-inch ruler.
If you find some problem areas, consult a piano technician (not a tuner) for help with repairs and adjustment. We strongly recommend that unqualified people not attempt repairs themselves. A piano is too large an investment to run the risk of damaging it in a misguided effort to "save money." Doing the things indicated above will not harm your piano, if they are done as indicated, and will help alert you to issues that could become worse later and may well affect your enjoyment of playing the piano.