Wild Air

About Keyboards

April 23rd, 2012

WARNING: TECHNICAL STUFF!   (If you aren’t interested in technical stuff, skip this one!)

Geometry:

There are two types of manual keyboards commonly found in organs, based on the position of the fulcrum point on which the keys pivot.   The best keyboards have long keys (usually 16″ or more), with the pivot point at the rear of the key.    Only about 1/3 of the length of the key is visible.        If the actions are  electric, the contact is usually under the key, about half-way back.     These are often called “rear pivot” keyboards, although a better description would be “long-throw.”

Other keyboards have short keys, with fulcrum points only a short distance behind the playing surface of the keys.   These keyboards have the advantage of taking up less space inside the console cabinet.   These short-throw keyboards are often called “center pivot.”

Although both types of keyboards can work well, most organists prefer long-throw keys.   There are two reasons.

First of all, consider the key as a lever.   With longer keys, the amount of force required to depress the key is more consistent with longer keys because the fulcrum is farther from the point where the force is applied.   On a short key, the force increases more dramatically as the player approaches the fulcrum, since the lever is shorter.   On a longer key, the difference in force is less because of the longer fulcrum.   The amount of force needed to depress any key is less at the bottom of the key (the end toward the player), and more  toward the top.   On a rear-pivot keyboard, the difference is much less, making the keys feel more consistent at whatever point the keys are depressed.

The second difference is angle.   When a key is depressed, it moves through an arc.   This arc is only a few degrees, and seems negligable on most good keyboards.   The pivot-point (fulcrum) of the key is the center of this arc, and the key itself is the radius.   A shorter key has a shorter radius, and, hence, a more noticeable angle.    

Finally, the speak-point of a longer key is easier to adjust, and therefore usually more accurate, on long keys than on short ones.

Materials:

Some keyboards are simply made of molded plastic.   These can vary in quality from poor to quite good.   The worst plastic keyboards have a light, hollow feel, with very little mass.   Better plastic keyboards are weighted to overcome this defect, and have a more natural feeling.   Almost all molded plastic keyboards are short-throw.   One advantage to high-quality plastic keys is that they are usually unaffected by humidity.

Although wood-core keyboards can be long or short throw, most are long-throw.   The key cores can be covered with plastic, bone, or exotic wood.   Unlike the bright-white Implex plastics used to cover keyboards a few decades ago, modern plastic key coverings can be realistic both in appearance and feel, and can be almost indistinguishable from much more costly bone coverings.   Wood coverings feel good and have a classy appearance, but often do not wear as well as plastic or bone.

Older keyboards may be covered in ivory or celluloid.   Ivory, of course, was used to cover keys for centuries until its purchase and use were banned.   The demand for this material nearly drove the African elephant to extinction.   Most piano and organ technicians (legally) salvage ivory material from older keyboards to replace missing or damaged coverings.   It should be noted that not all ivory keyboards were created equal.   While many have thick, carefully tooled coverings, others had very thin ivory that can crack, chip, or fall off.

Celluloid was invented in 1862, and was in common use by the turn of the twentieth century as a cheaper replacement for ivory.   It can often be distinguished from ivory by the simulated grain, which usually very straight and regular.   Celluloid was consider the first thermoplastic.   The two drawbacks to its use were that it discolors and decays over time, and that it is flammable.   To the writer’s knowledge, it is not used for keyboards today.   It is often found in reed organs and pipe organs produced before World War II.  

Organ keyboards today are often supplied with “tracker” or toggle touch.   Like harpsichords, tracker organs have a “pluck point,” a point in the stroke of the key when the resistance decreases suddenly.   In tracker organs, this is the point at which the pressure of the key overcomes the wind resistance on the pallet.   Once the pallet has broken loose, the force required to fully open it becomes less.   This pluck or toggle makes the action of the keyboard feel more definite to the player.   Toggle touch is produced with either a toggle spring or by making the key work against a magnetic field at the beginning of its travel.

So, there is everything you ever wanted to know about keyboards!

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