Electronic keyboard
An electronic keyboard (also called digital keyboard, portable keyboard and home keyboard) is an electronic or digital keyboard instrument.
The major components of a typical modern electronic keyboard are:
- Musical keyboard: The plastic 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)
- Rhythm & chord generator: A software program which produces rhythms and chords by the means of MIDI electronic commands.
- Sound generator: An electronic sound module typically contained within an integrated circuit or chip, which is capable of accepting MIDI commands and producing sounds.
- Amplifier and speaker: a low-powered audio amplifier and a small speaker that amplify the sounds so that the listener can hear them.
History
Electronic keyboard is combination of processes of pressing mechanical keys and producing sounds by means of electric circuitry.
In the 12th century clavichord and harpsichord were developed. As technology got developed more sophisticated and standard keyboard got developed with 12-tone keyboard. In the 18th century, the piano was adopted which allowed a new way of controlling volume by varying the force of the press.
The next step was to develop electronic sound technology. The first musical instrument was 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 clavecin electrique. This was keyboard instrument incorporated with plectra and activated by electricity.
But both instruments was not using electricity to produce sound. Elisha Gray invented first analog electronic synthesizer called musical telegraph. It was making sound from electromagnetic circuit's vibration. He incorporated basic single note oscillator.Next he added loudspeaker consisting of diaphragm to make data audible.
In 1906, Lee de Forrest invented the triode electronic valve. In 1915 he invented the first vacuum tube instrument the audio piano. Then until the invention of transistor, the vacuum tube was essential component in electric instruments.
In 1935, the hammond organ was introduced. It was capable of producing polyphonic sounds.Next development was Chamberlin Music Maker in late 1940s and Mellotron in early 1950s.
The first step towards the electronic piano was by Rhodes with the pre-piano. It was a three and a half octave instrument. The next generation was capable of doing self-amplification. In 1955, the Wurlitzer Company released first electric piano ,the 100.
The invention of the musical synthesizers in the 1960s was a step ahead towards the modern keyboard. As technology became more developed, huge synthesizers evolved into portable instruments that could be used in live shows.
This began in 1964 when Bob Moog produced his moog synthesizer. It did not have the same keyboard but its next generation was equipped with a built-in keyboard. The keyboard was able to produce only one tone. Some instruments such as the EML 101, ARP Odyssey, and the Moog Sonic six could produce two different tones at once when two keys were pressed. The next number of electronic keyboards produced which were combination of organ circuits and synthesizer processing. These were Moog’s Polymoog, Opus 3, and the ARP Omni.
The invention of the musical instrumental digital interface(MIDI) as a standard for digital code transmission digital technology development caused great development in keyboard technology. Manufactures such as Casio, Yamaha, Korg, Rolland, and Kurzweil are producing well built, lightweight, cheap, and clear sounding instruments[1].
Classification
Some manufacturers and retailers (for example: Yamaha) divide their keyboard products into the following categories:
- Digital Pianos - "Full-sized keyboards that sound and feel like an acoustic piano".
- Stage Pianos - "Professional performance for the studio and stage".
- Synthesizers - "Unlimited creative potential for any style of music".
- Digital keyboards - "Hundreds of voices and sounds … interactive tutorials … Portable".
Compared to digital pianos or stage pianos, digital keyboards are usually much lower in cost, have unweighted keyboards 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: 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. When the on-board rhythm track is turned on, the auto-chords will be played automatically in the tempo of the rhythm track.
- 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 and 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 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.
- Style: Pre-programmed "styles", usually depend on the chord given by the player, 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. For example, if the "jazz" style is selected, the keyboard would play seventh and ninth chords in a characteristic jazz "comping" rhythm.
- Synchronization: Usually, styles compose of two to four sections, so adding transition effects, called syncs, smooth the transition between sections and improve the rhythm of the effect.
- 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 spring-loaded.
- 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.
Internal Circuitry
The Piano uses levers, hammers and strings to make sound at various pitches.But electric keyboard makes this possible by using Microprocessor and other signaling circuitry.Though electronic keyboard is very user friendly , its internal circuitry is very complex[2].
Various keyboards have number of keys. Musical keyboard has keys for various pitches. Computer keyboard has keys for alphabets, symbols. considering 61 keys there is need of 62 wires to send signal to integrated circuit. So Keyboard matrix (music) is used.It has matrix of 8 rows and 8 columns. By using this there is need of only 16 wires to send signal instead of 62. When key is pressed Keyboard controller scans every column for pressed key and then it scans every row in that column.And determines which key is pressed. Then it sends appropriate signal to integrated circuit. This keyboard matrix can also be used for non musical keyboard.Keyboard matrix simplifies circuit greatly[3].
In musical keyboard, when key is pressed ,
Pitch of the sound depends on frequency of square wave.Pitch is directly proportional to input frequency.Pitch is determine by the integrated circuit(LM324) and resistor,capacitor network. When key is pressed
- Capacitor starts charging and LM324 output is 6V corresponding to positive part of square wave.
- When it reaches its maximum value, it starts discharging and output is 0 V corresponding to negative part of square wave.
- If still key is pressed then capacitor starts charging again.
- And square wave of 6-0-6-0-6-0 occurs.
This square wave produces buzzing tone. Thus pitch of tone depends on charging -discharging time. When charging is quicker then frequency is higher so the pitch and other way round.Charging time can be given by τ=RC.Thus frequency also depends on resistance in series with key[4].
Another mechanism is using microprocessor chip. When key is pressed
- Tiny metal tab under key get pressed.
- This completes one electric circuit due to contact.
- And this send signal to central circuitry.This circuitry consist of transistors, microchips,resistors. It has thousands of sounds store in its memory.
- When it receives particular signal for particular key its job is to send appropriate signal to speaker circuitry to make particular sound[2].
In case of push button switches the main difficulty is switch bounces for substantial time period. Due to this bouncing there can not be correct detection of input data. So there is debouncing mechanism provided.There are two ways:
- Software mechanism- In this microchips are programmed to wait switch bouncing gets completed.
- Hardware mechanism-There is extra circuitry to debounce switch.
As digital technology is developing fast, keyboard technology is also using this technology nowadays. The invention of the musical instrumental digital interface(MIDI) as standard for digital code transmission digital technology development causes great development in keyboard technology. Manufactures such as Casio, Yamaha, Korg, Rolland, and Kurzweil are producing well built, lightweight,cheap,versatile,clear sounding instruments using digital technology[1].
MIDI controls
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. These are often called "sustain pedals" by keyboardists, as their most common function is to simulate the sustain pedal 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[5].
A partial list of manufacturers
References
See also