On Synthesizers: In Search of the Ideal Synthesizer Keyboard

April 11, 2016

Continuing our celebration of 40 years of Keyboard, we are presenting Bob Moog's original "On Synthesizers" columns in their entirety. Today's edition comes from the November 1984 issue.

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Much of my recent work has been in the design of keyboard actions, those parts of a keyboard that account for its 'feel.' An important part of this work is simply talking to keyboard players to learn what kind of feel they like best, and how players' keyboard preferences are related to the kind of music they play and to their general approach to keyboard performance. What has emerged is growing evidence that there may be no one action design that is optimized for all types of keyboard performance.

Conventional Keyboard Actions. A wide variety of keyboard actions to link the player to his tone sources has been developed over the centuries. Early pipe organs provided direct linkages from the keys to the pipe valves. In contrast to the electrically or pneumatically actuated pipe valves of modern pipe organs, these early 'tracker action ' organs enabled the player to shape soft or hard attacks by how rapidly he or she pressed the keys. Tracker organs are still being made and performed on.

Another early keyboard instrument with expressive touch sensitivity was the clavichord.
In this instrument, a wedge-shaped 'tangent' attached to the key lever hits the string when the key is depressed. The harder the key is depressed, the louder the sound is. In addition to dynamic control, the clavichord action allows the player to bend pitch. How? By pressing on the key after the tangent is in contact with the string, the player stretches the string and raises the pitch.

Modern (that is, industrial) technology has largely bypassed the delicate nuance of the tracker organ and the clavichord, which were well suited to the sedate environments of the clergy and nobility of antiquity, in favor of keyboard instruments whose sounds fill large concert halls and churches. Today's most familiar keyboard instruments are the piano and the pipe organ. Keyboards for these instruments are in regular production in factories around the world, which, I assure you from first-hand experience, is the reason that synthesizers are now equipped with organ-like or piano-like keyboards.

The Organ Keyboard. Keyboards of pipe and electronic organs have the simplest actions of all. When you depress an organ key, generally only one part moves —the key lever that you put your finger on. When the key lever is depressed, an electrical switch, either underneath the front of the lever or over the end of the lever behind the balance rail, is actuated, thereby starting the sound. Keyboards of conventional organs provide only on/off control, so they are optimized to move up and down rapidly. Usually, some sort of spring is employed to return the key lever to its rest position as quickly as possible.

In some high-class organs, a toggle mechanism is attached to the back of the key lever. The toggle provides a slight 'snap' as the key descends, something like the snap of a toggle switch when it is flipped. If properly designed, a toggle mechanism actually makes the keyboard easier to play rapidly. This is because, with a toggle-action keyboard, it takes more force to push a key down than it does to keep it down, thus allowing the player to put more energy into initiating notes and less into keeping them sustained. Interestingly, the fastest typewriter keyboards are also those that have a slight toggle in their feel.

The Piano Keyboard. In contrast with organ keyboards, piano keyboards allow players to control the intensity of a tone by how hard they hit the key lever. In a conventional acoustic piano action, the key lever is used to set a hammer into high-velocity motion. At the end of the lever's travel, the hammer separates from the key lever linkage (like the next stage of a multi-stage rocket), and then flies freely until it hits the string. A physicist, using technical terms, would say that there is an energy transfer from the player's finger, through the key lever, to the hammer. To a physicist, 'energy' is not a vague, qualitative term (as it is when you say 'high energy groove’). The energy of mechanical motion is called 'kinetic energy' and is something that can be transferred from one moving object to another in a complex mechanical system like a keyboard. What happens is that the kinetic energy of the hammer is nearly completely transferred to the string, thereby initiating the string's vibration. When the hammer bounces back from the string, it has much less kinetic energy, and what it has is absorbed by the complex assemblage of action parts. The dozens of parts in a typical acoustic piano action are not there only to transfer energy from player to hammer.

They are there to insure that (a) the hammer is free from the key lever as it hits the string, (b) the player feels almost nothing when the hammer rebounds, and (c) the key lever and hammer return to their rest positions as quickly as possible.

Acoustic pianists depend on the feel of their instruments' keyboards to know how much kinetic energy their fingers are sending to the hammers. They must know this as they depress the key. Once the key is down, it is too late! Keyboard designers call this 'tactile feedback.' It is of crucial importance in enabling players to control the dynamics of their performance.

Electronic Instrument Keyboards. The first keyboard synthesizers used stock electronic organ actions. Most currently available synths still use this type of keyboard. Back twenty years ago, we were too busy focusing on getting reliable switch contacts that didn't interfere with the smooth feel of the key motion to worry very much about the keyboard itself. Since we tended to use keyboard designs that were already in use in home organs, and since home organ keyboards generally use light springs suitable for playing by one-finger virtuosi, many professional keyboardists found the keyboards of these early instruments 'weak,' sloppy, and 'hard to play.' By the time we (at my old company) got around to doing the Minimoog, we knew better. The Minimoog keyboard requires three ounces of force to push a key, about the same force that it takes to get an acoustic piano key moving, and twice the force that it takes to depress a key on some of the early home organ keyboards.

Today's 'organ-style' (i.e. non-weighted, single-piece action) keyboards for electronic instruments have undergone further engineering. In some instruments, metal switch contacts have been replaced by membrane switches, conductive rubber, or magnetic sensors. Inexpensive plastic keyboards are in wide use, especially in miniature and portable instruments. If you're interested in non-velocity-sensitive keyboards, virtually any instrument that makes it to your musical instrument retailer is likely to have a fast, smooth keyboard.

If, on the other hand, you are interested in velocity or pressure sensitivity, you will have to make some compromises. Next month's column will talk about just what those compromises are.

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