The major components of a typical modern electronic keyboard are:
- Musical keyboard: The white and black piano-style keys which the player presses, thus connecting the switches, which triggers the electronic note or other sound. Most keyboards use a keyboard matrix circuit to reduce the amount of wiring that is needed.
- User interface software: A program (usually embedded in a computer chip) which handles user interaction with control keys and menus, which allows the user to select tones (e.g., piano, organ, flute, drum kit), effects (reverb, echo, telephones or sustain), and other features (e.g., transposition, an electronic drum machine)
- Computerized musical arranger: A software program which produces rhythms and chords by the means of computerized commands, typically MIDI.
- Sound generator/sound chip: An electronic sound module or a musical synthesizer typically contained within an integrated circuit or chip, which is capable of accepting MIDI commands and producing sounds.
- Amplifier and speaker: a low to middle-powered audio amplifier and speakers that amplify the sounds so that the listener can hear them.
Keyboard instruments can be found as far back as the hydraulis in the 3rd century BCE, which developed into the pipe organ, and small portable instruments such as the portative and positive organ. Additional keyboard instruments, the clavichord and harpsichord, were developed in the 14th century CE. As technology improved, more sophisticated keyboards were developed, including the 12-tone keyboard still in use today. Initially, the keyboard of an instrument could only produce sounds of one particular volume. In the 18th century, the pianoforte was invented, which allowed a new way of controlling volume by varying the force of the keypress.
The next step was to develop electronic sound technology. The first musical instrument was the Denis d'or, which was built by Vaclav Prokop Dovis in 1753. It was incorporated with 700 strings temporarily electrified to enhance their sonic qualities. In 1760, Jean Baptiste Thillaie de Laborde developed the clavecin électrique. This was a keyboard instrument incorporated with plectra and activated by electricity.
But both instruments were not using electricity to produce sound. Elisha Gray invented a electric musical instrument called musical telegraph. It made sound from an electromagnetic circuit's vibration. He incorporated a basic single note oscillator. Next he added a loudspeaker consisting of diaphragm to make data audible.
In 1906, Lee de Forest invented the triode electronic valve. In 1915 he invented the first vacuum tube instrument, the audio piano. Then, until the invention of the transistor, the vacuum tube was an essential component in electric instruments.
In 1935, the Hammond organ was introduced exploiting previous limited production efforts like the Robb Wave Organ from 1923. It was capable of producing polyphonic sounds by virtue of a spinning shaft with many magnetic 'lobes' which would cycle past a pickup at a rate that would produce each desired tone. "Tone Wheel Organ" is the general name for this technology.
In 1939 Hammond also introduced the Novachord which uses about 170 vacuum tubes, coils, capacitors and resistors largely to create an upper octave of notes then divide them in half using 'flip flop' circuits to create successively lower octaves from each note. But the instrument also has many features like envelopes for filter and amplifiers so that sounds can be contoured at the user's discretion. Making it the first production analog synthesizer.
In 1941 George Jenny's previously prototyped Ondioline became the first truly portable synthesizer keyboard (the Novachord weighted over 500 pounds (230 kg).)
More developments were made with the Chamberlin Music Maker in late 1940s and the Mellotron in the early 1950s, which employed mechanisms to play back recordings at speeds that would produce the desired tone for the key being struck. Other technologies improved on this idea over the years. Machines like the Optigan used photo-emulsion to create disks that had images whose density would covert to waveforms when spun in front of a beam/sensor assembly. And finally in 1981 the E-mu Emulator was marketed to digitally store samples and play them back.
The first step towards the electronic piano was by Harold Rhodes who developed various prototypes using parts from B-17 aircraft that were being scrapped. Harold received a medal since the resulting keyboard was used as therapy for people rehabilitating from injuries from WW2. (It is small enough to set on a stand over people's bed in a hospital, looking something like a miniature grand piano in shape.) Instructions were made and people built this "pre-piano" which amplifies the signals generated in a pickup from the vibration of Stainless Steel rods tapered near the steel base they are driven into holes in. And piano type wooden hammers are used to strike them. It was a three octave (E to F for 38 notes) instrument in the version I have in my shop. There may be other versions since people were free to modify the instructions. A tube amplifier drove a speaker pointing out the bottom.
In 1955, the Wurlitzer Company released the first electric piano, the model 100. The wurlitzer strikes flat tines whose vibration is amplified from a surrounding electrostatic charged 'comb'. In '59 the Fender company bought the Rhodes name and produced the  and then in the mid '60s began producing the famous Fender Rhodes series which used rod shaped tines mounted on a steel piece that runs parallel above them, with a coil pickup on each individual tine.
The invention of the transistor in 1959 spawned the production of progressively more compact keyboards. Many home organs maintained the appearance but lost some weight due to the lower power consumption needs of transistor circuitry. Also in this era 'combo organs' found a lot of use like the famous Vox Continental used by the Beatles and others, the Gibson G101 used by the doors, and others by Farfisa, Wurlitzer, Acetone (Roland) and others. These were usually built using 12 oscillators and transistor pair 'divider' circuits to produce all the frequencies like all non- 'tone wheel' electronic organs of the era. They were just more compact and thus suited for 'combo' use.
The exploration of musical synthesizers in the 1960s was a step towards the modern keyboard. As technology became more developed, huge synthesizers evolved into portable instruments that could be used in live shows.
The rapid accumulation of momentum began in 1964 when Bob Moog produced his Moog synthesizer. It used a remote keyboard and was 'modular' in design. (ie. it was a rack that held boxes which each had a function. At least one to create a tone controlled in pitch by a voltage input. And usually a host of other modules including Filter(s), Amplifier(s), Envelope Generator(s) etc. ) His next generation was equipped with a built-in keyboard in 1970; the Mini-Moog. These keyboards were monophonic, along with semi-modulars like the ARP2600, and were only able to respond to one note at a time. (Though 3 oscillators could be layered together in response to the 'control voltage' produced by that note.)
In 1972, instruments such as the EML 101, ARP Odyssey, and Moog Sonic six were duo-phonic meaning they could produce two different tones at once when two different keys were pressed. And in 1974 Oberheim produced the first polyphonic synthesizer using their SEM Modules (which were originally designed to allow musicians to just layer more complex sounds together in a monophonic 'stack'. ) They produced a key assigner circuit that would assign a note to one of several SEM modules. (They came in 2, 4 and 8 voice racks eventually.) When more notes got hit than the number of racks available the latest note would have to 'steal' one of the SEM modules from the note it had been assigned to. These polyphonic synthesizers were very popular eventually and Yamaha produced the CS-50 in 1976 which had four voices that didn't have to be individually programmed in order for them to sound the same. And a sea of other entries followed
In 1970 Ken Freeman demonstrated the first 'string machine' which was essentially combo-organ like in size and how it generated tones. It had simple controls though centered around creating an ensemble effect where vibrato is happening at slightly different rates on different notes like in a real orchestra. Ken used 6 discrete LFO's (low frequency oscillator circuits) to modulate atypically hit together note combinations (diminished fifth combinations like C and F#). It had two 'ranks' of 12 oscillators plus a single oscillator driving a chip that develops the top octave of notes in the version that hit market in 1974. In November 1974 the British patent 1,509,530 lists an electronic digital musical arranger by Nicholas Kenneth Kirk. Sadly due to bad negotiations with the eventual manufacturer CMS, the product did not hit market until right after the ARP Solina String Ensemble and Crumar Stringman, which used instead a much less expensive approach. (Though not quite as good sounding some would claim since the approach uses digitally clocked chips called BBD's. ). So only a few hundred were made.
In 1975 the turn towards building a synthesizer of sorts over an organ came to fruition in Moog’s Polymoog. Many patents exist from this keyboard. It incorporated velocity sensitivity for one thing. Each note had its own circuit board with a VCF/VCA chip so that it was truly fully polyphonic. Many were disappointed that the filter lacked the facilities of the more flexible moog filter used in other keyboards. And that there were so many connectors and they were not all that reliable.
Also in 1975 Crumar of Italy produced the "Multiman" which also was an organ with synthesizer facilities. It had a bass option, a brass with filter controls and simple envelope, a piano and clavi preset, and a couple string tabs with decay control and vibrato control. The first of what we might call the 'Swiss army knife' synthesizer. In 1976 the ARP Omni combined a more limited synthesizer with a string machine and bass also and became ARP's biggest seller. Also in 1976 the Korg PE-1000 used an individual saw oscillator for each note.
In 1977 the Yamaha CS-60 and CS-80 began to implement 'memory'. However it was merely an alternate set of sliders that hid under a hatch. In 1978 however the OB-1 from Oberheim gave actual electronic storage of the sound settings. The Sequential Circuits Prophet-5 the same year offered this feature in a five voice polyphonic synthesizer. Dave Smith's company began to skyrocket to fame as they also developed some other firsts.
But the ARP engineers were acquired by Fender when they bought the mismanaged company in 1979. And they complete the Fender Rhodes Chroma, the first computer controlled keyboard. Released in 1981, an Apple computer could be used to run sequencing software that allowed the user to easily program which notes were being hit at particular instants in the song production. THe 'Chroma' port only appeared on the successor though. The Chroma Polaris in 1984.
Dave Smith's company found interest in a cooperative effort with Roland. The invention of the musical instrumental digital interface(MIDI) as a standard for digital code transmission digital technology development spurred on more great development in keyboard technology. As now keyboards from totally different manufacturers who participated could communicate through an inexpensive cable! The Sequential Circuits Prophet 600 and the Roland Jupiter 6 spoke to one another at the NAMM trade show and Yamaha soon had the standard implemented into their DX synthesizers which would outsell all previous keyboards.
The DX7, the most well known had a good feeling keyboard (something that had only appeared in a few like the CS-80 in the synthesizer domain to date), entirely digital circuitry leaving it free from the need of calibration, and vast numbers of parameters that could be accessed. The "FM" (frequency modulation) synthesis method was something that had not been explored to near this depth. Most synthesizers before this were subtractive. ie. You start with a very harmonic-laden sound and you selectively subtract from them using low, high or bandpass filters, or some other methods that tended to result in stranger sounds like ring modulation.
Also in 1983 Dave Smith's company SCI marketed the first polyphonic synthesizer keyboard that could play more than one sound at a time called the 'Six-Trak'. It had a six track sequencer and each track could access a different sound. The same year the SCI Prophet T8 with optical key sensing became the first piano action emulating midi keyboard.
But the remaining companies after ARP's demise that had produced analog synthesizers rapidly began to feel the stress. Roland and Korg also of Japan maintained with some innovations of their own and each had 'hit' keyboards (the D50 from Roland and M1 from Korg in the later 1980s) I've heard that total DX series unit sales were on the order of 1 Million. The others from Roland and Korg over 250,000.
I remember seeing the patent for digital sample playback from 1982 I recall but I can't find it now. Someone please provide the reference for when the first patent was applied for. But the D50 and M1's success were riding on the back of the Kurzweil K250 which first really applied this technology well in 1984. This machine was the first full digital workstation with facilities to sample acoustic sounds with a microphone. And play them back with a rate that is proportioned for the note being struck. Many great samples were included in the unit including a piano sound that is still used today by many artists. And the samples can be routed through a synthesizer architecture of some kind.
Initially some companies steered away from emulating the subtractive synthesis in the digital realm because it was difficult to model how a filter would respond to these complex signals. By the early '90s some fairly good implementations were beginning to appear. The Peavey DPM series also touted as the first keyboards that could import samples which were not 'sampling keyboards'. They also were the first to use off the shelf DSP chips I've read from the interview with Hartley Peavey. And in my opinion the first that began to do a semi-decent job emulating the response of analog filters.
This Sample playback technology also spawned a vast number of inexpensive consumer units which commonly appear in thrift stores and consumer outlets. As the price of memory began to plummet every company was making keyboards around this idea. Casio and Yamaha have led sales in these types of units which feature built in speaker systems, usually can run from batteries or power adapters, and have a library of samples with very limited editing if any. They often use cheap plastic strips of keys even to keep cost down.
On a different note, the Kurzweil K150 and the Kawai K5 explored additive synthesis where harmonics can be proportioned to make different tones while enveloping groups of them differently in the mid '80s. RMI had explored this to a limited extent in 1974 with the harmonic synthesizer they produced. It should also be mentioned that they were producing the earliest electric piano machines in 1970. This less common synthesis method is also used in Kawai's last synthesizer product series, the K5000's from 1996. Organs like the Hammond B3 use drawbars to control harmonic content of the tone. But the K5000 has an envelope for each harmonic in the entire audio spectrum and dynamic filter control over that for vast possibilities in sound creation.
So there are many approaches to making electronic keyboards. In more recent history things have branched two directions. There are many who like myself can hear greater value in instruments that avoid computer modeling and digital involvement in the signal path in general. In the analog realm there are real voltages having interplay with real circuits that have analogous aspects to things that occur in the mechanical realm. Eg. when a guitar sting is plucked and a myriad of different elements come into play to produce the sound we hear. And the artist can use these elements to introduce their own expressive nature into the instrument, breathing life into the music.
In the digital realm, only the things the people who designed the hardware are available to us. And those of course lack the natural subtle nuances that the incredibly complex nature we dwell in affords to the person playing an acoustic instrument or an analog synthesizer. So the sounds often have an initial impression because they can be arbitrarily unusual. However over time the sounds tend to be perceived as 'sterile' and lacking life. The value of many wonderful analog instruments plummeted in the mid '80s when the digital crazy hit. I own a Memorymoog which a guy traded a 100 dollar guitar in the late 1980s. In 2014 just the chips in the instrument are valued at over 2500 dollars. There has been a resurgence of interest in these instruments since the '90s really and some manufacturers have entered production again with some new features afforded by the advances in technology that have taken place since analog dominated. Some machines have extensive upgrades that can be installed like the Memorymoog, Roland Jupiter 4 and 6, SCI Prophet 600, Roland Juno 60, Korg Mono/Poly, Korg DSS-1.
The other branch has been towards modeling instruments and software that can interface with a controller keyboard plugged into the computer or just software on the computer. Programs exist that help people collaborate work where they can even play things together from remote locations etc. Many people today produce incredible music just using a computer. It is still not the same as having the actual instruments in front of you but it is getting better as people continue to refine the process.
Some manufacturers and retailers divide their keyboard products into the following categories:
- Digital piano - Electronic keyboards designed to sound and feel like an acoustic piano. In most cases they can fully replace acoustic pianos and provide several features, such as recording and saving files to a computer. They are also less sensitive to the climate changes in room. And there is also no need for tuning unlike in the case with acoustic pianos.
- Stage piano - A type of digital piano designed for stage or live band use.
- Synthesizer - Electronic keyboards that uses various sound synthesis to produce a wide variety of sounds.
- Arranger - Electronic keyboards that can produce a range of sounds as well as backing accompaniments accompany the performer, and is usually played by the left hand. An arranger keyboard player is usually called one-man bands.
Compared to digital pianos or stage pianos, digital keyboards are usually much lower in cost, have unweighted keys but have a great many ancillary controls and usually feature on-board loudspeakers. Unlike synthesisers, the primary focus is not on detailed control of sound synthesis parameters.
Concepts and definitions
- Auto accompaniment / chord recognition: Auto accompaniment is used on programmed styles to trigger specific chords that will sound when a single key is pressed on the keyboard. For example, when the auto accompaniment feature is on, and the performer presses a "C" note in the low range of the keyboard, the auto accompaniment feature will play a C Major chord. In many keyboards, the auto accompaniment feature will play the automatic chords in a rhythm and style that is appropriate for the musical style (e.g., rock, pop, hip-hop) selected by the performer (see the Accompaniment styles section for more). When the on-board rhythm track is turned on, the auto-chords will be played automatically in the tempo of the rhythm track. Many keyboards have an option to form on-bass chords, as well as many other complex chords.
- Demonstration: Most keyboards have pre-programmed demo songs. As the name "demo" implies, one usage of these pre-programmed songs is for a salesperson to use to demonstrate the capabilities of the keyboard, in terms of its different voices and effects. The demo songs can also be used for entertainment and learning. Some keyboards have a teaching feature that will indicate the notes to be played on the display and wait for the player to press the right one.
- Touch sensitivity (also found under the keyword velocity in some manuals): While the least expensive keyboards are simply "on-off" switches, mid-range and higher-range instruments simulate the process of sound generation in chordophones (string instruments) which are sensitive to the pressure (or "hardness") of a key press. Mid-range instruments may only have two or three levels of sensitivity (e.g., soft-medium-loud). More expensive models may have a broader range of sensitivity. For implementation, two sensors are installed for each key: the first sensor detects when a key is beginning to be pressed and the other triggers when the key is pressed completely. On some higher-end electronic keyboards or digital pianos, a third sensor is installed. This third sensor allows the player to strike a key and still sound a note even when the key has not yet come to its full resting position, allowing for faster (and more accurate) playing of repeated notes. The time between the two (or three) signals allows a keyboard to determine the velocity with which the key was struck. As the key weight is constant this velocity can be considered as the strength of the press. Based on this value the sound generator produces a correspondingly loud or soft sound. The least sophisticated types of touch sensitivity cause the keyboard to change the volume of the instrument voice. The most sophisticated, expensive types will trigger both a change in volume and a change in timbre, which simulates the way that very hard strikes of a piano or electric piano cause a difference in tone—as well as an increase in volume. Some sophisticated touch-sensitivity systems accomplish this by having several samples of an acoustic instrument note per key (e.g., a soft strike, a mid-level strike, and a hard strike). Alternatively, a similar effect can be accomplished using synthesis-modelling of the ASDR envelope or digital modelling (e.g., for the hard strike, the keyboard would add the timbres associated with a hard strike—in the case of a Fender Rhodes voice, this would be a biting, "bark" sound).
- After-touch: A feature brought in the late 1980s (although synthesizers like the CS-80 extensively used by artists like Vangelis featured after-touch as early as 1977) whereby dynamics are added after the key is hit, allowing the sound to be modulated in some way (such as fade away or return), based upon the amount of pressure applied to the keyboard. For example, in some synth voices, if the key continues to be pressed hard after the initial note has been sounded, the keyboard will add an effect such as vibrato or sustain. After-touch is found on many mid-range and high-range synthesizers, and is an important modulation source on modern keyboards. After-touch is most prevalent in music of the mid to late 1980s, such as the opening string-pad on Cock Robin's When Your Heart Is Weak, which is only possible with the use of after-touch (or one hand on the volume control). After-touch is not normally found on inexpensive, beginner-level home keyboards.
- Polyphony: In digital music terminology, polyphony refers to the maximum number of notes that can be produced by the sound generator at once. Polyphony allows significantly smoother and more natural transitions between notes. Inexpensive toy electronic keyboards designed for children can usually only play one note at a time. Many low priced keyboards can perform four or five notes at a time. Better-quality keyboards can perform over ten notes at a time with 32 or 64 notes being common.
- Multi-timbre: The ability to play more than one kind of instrument sound at the same time. Such as with the Roland MT-32's ability to play up to eight different instruments at once.
- Split point: The point on a keyboard where the choice of instrument can be split to allow two instruments to be played at once. In the late 1980s it was common to use a MIDI controller to control more than one keyboard from a single device. The MIDI controller had no sound of its own, but was designed for the sole purpose of allowing access to more sound controls for performance purposes. MIDI controllers allowed one to split the keyboard into two or more sections and assign each section to a MIDI channel, to send note data to an external keyboard. Many consumer keyboards offer at least one split to separate bass or auto-accompaniment chording instruments from the melody instrument.
- Accompaniment styles: Pre-programmed musical accompaniment styles (also called rhythm, backing or pattern by some manufacturers), consist of a variety of genres for the player to use (e.g., pop, rock, jazz, country, reggae). The keyboard plays a chord voicing and rhythm which is appropriate for the selected genre. In general, accompaniment styles usually imitates the sound of a full band or an orchestra. Certain keyboards may include a feature that allows the performer to create, compose and customize their own accompaniments. This feature is usually called a pattern sequencer, rhythm composer, or a style creator.
- Accompaniment sections and synchronization: Usually, styles compose of two to four sections, as well as fill-in patterns, introduction/ending patterns, and various synchronizations to improve the effects of the accompaniment.
- Tempo: A parameter that determines the speed of rhythms, chords and other auto-generated content on electronic keyboards. The unit of this parameter is beats per minute. Many keyboards feature audio or visual metronomes (using graphics on a portion of the display) to help players keep time.
- Auto harmony: A feature of some keyboards that automatically adds secondary tones to a note based upon chords given by the accompaniment system, to make harmony easier for players who lack the ability to make complex chord changes with their left hand.
- Wheels and knobs: Used to add effects to a sound that are not present by default, such as vibrato, panning, tremolo, pitch bending, and so on. A common wheel on contemporary keyboards is the pitch bend, adjusting the pitch of a note usually in the range of ±1 tone. The pitch bend wheel is usually on the left of the keyboard and is a spring-loaded potentiometer.
- Keyboard response: Weighted or spring-loaded keys. The least expensive home keyboards have no keyboard response, and they use plastic keys that are mounted on soft rubber or plastic pads. This set-up, called "synthesizer action" is also used in synthesizers. "Weighted response" refers to keys with weights and springs in them, which give a "hammer action" feel similar to an acoustic piano. Most electronic keyboards use spring-loaded keys that make some kinds of playing techniques, such as backhanded sweeps, impossible, but make the keyboards lighter and easier to transport. Players accustomed to standard weighted piano keys may find non-weighted spring-action keyboards uncomfortable and difficult to play effectively. Conversely, keyboard players accustomed to the non-weighted action may encounter difficulty and discomfort playing on a piano with weighted keys.
Electronic keyboards typically use MIDI signals to send and receive data, a standard format now universally used across most digital electronic musical instruments. On the simplest example of an electronic keyboard, MIDI messages would be sent when a note is pressed on the keyboard, and would determine which note is pressed and for how long. Additionally, most electronic keyboards now have a "touch sensitivity", or "touch response" function which operates by an extra sensor in each key, which estimates the pressure of each note being pressed by the difference in time between when the key begins to be pressed and when it is pressed completely. The values calculated by these sensors are then converted into MIDI data which gives a velocity value for each note, which is usually directly proportional to amplitude of the note when played.
MIDI data can also be used to add digital effects to the sounds played, such as reverb, chorus, delay and tremolo. These effects are usually mapped to three of the 127 MIDI controls within the keyboard's infrastructure — one for reverb, one for chorus and one for other effects — and are generally configurable through the keyboard's graphical interface. Additionally, many keyboards have "auto-harmony" effects which will complement each note played with one or more notes of higher or lower pitch, to create an interval or chord.
DSP effects can also be controlled on the fly by physical controllers. Electronic keyboards often have two wheels on the left hand side, generally known as a pitch bend and a modulation wheel. The difference between these is that the pitch bend wheel always flicks back to its default position — the center — while the modulation wheel can be placed freely. By default, the pitch bend wheel controls the pitch of the note in small values, allowing the simulation of slides and other techniques which control the pitch more subtly. The modulation wheel is usually set to control a tremolo effect by default. However, on most electronic keyboards, the user will be able to map any MIDI control to these wheels. Professional MIDI controller keyboards often also have an array of knobs and sliders to modulate various MIDI controls, which are often used to control DSP effects.
Most electronic keyboards also have a socket at the back, into which a foot switch can be plugged. The most common function is to simulate the sustain on a piano by turning on and off the MIDI control which adds sustain to a note. However, since they are also simple MIDI devices, foot switches can usually be configured to turn on and off any MIDI control, such as turning of one of the DSP effects, or the auto-harmony.
- British Patent no. 1,509,530 by Nicholas K. Kirk filed 19th. Nov. 1974. - Apparatus for recording and replaying music.
- piano bass
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