Electronic keyboard
An electronic keyboard, portable keyboard, or digital keyboard is an electronic musical instrument, an electronic derivative of keyboard instruments. Electronic keyboards include synthesizers, digital pianos, stage pianos, electronic organs and digital audio workstations. In technical terms, an electronic keyboard is a synthesizer with a low-wattage power amplifier and small loudspeakers. Electronic keyboards are capable of recreating a wide range of instrument sounds (piano, Hammond organ, pipe organ, violin, etc.) and synthesizer tones with less complex sound synthesis. Electronic keyboards are usually designed for home users, beginners and other non-professional users. They typically have unweighted keys. The  least expensive models do not have velocity-sensitive keys, but mid- to high-priced models do. Home keyboards typically have little, if any, digital sound editing capacity. The user typically selects from a range of preset "voices" or sounds, which include imitations of many instruments and some electronic synthesizer sounds. Home keyboards have a much lower cost than professional synthesizers. Alesis, Casio and Yamaha are among the leading manufacturers of home keyboards. Terminology. An electronic keyboard may also be called a digital keyboard, or home keyboard, the latter often refers to less advanced or inexpensive models intended for beginners. The  obscure term "portable organ" was widely used in Asian countries to refer to electronic keyboards in the 1990s, due to the similar features between electronic keyboards and electronic home organs, the latter of which were popular in the late 20th century. In Russia, Belarus and Ukraine, most types of electronic keyboards (including digital pianos and stage pianos) were simply often referred to as a "synthesizer" (Russian: синтезатор, "sintezator"), usually with no other term to distinguish them from actual digital synthesizers. The term "electronic keyboard" may also be used to refer to a synthesizer or digital piano in colloquial usage Components . The major components of a typical modern electronic keyboard are: Classifications. Conventional home keyboards differ from other electronic keyboards due to the design, features and target market: Compared to digital pianos or stage pianos, digital home keyboards are usually much lower in cost, as they have unweighted keys. Like digital pianos, they usually feature on-board amplifiers and loudspeakers. Stage pianos, however, typically do not have integrated amplifiers and speakers, as these instruments are normally plugged into a keyboard amplifier in a professional concert setting. Unlike synthesizers, the "primary" focus of home electronic keyboards is not on detailed control or  creation of sound synthesis parameters. Most home electronic keyboards offer little or no control or editing of the sounds (although a selection of 128 or more preset sounds is typically provided). MIDI controls. MIDI, Musical Instrument Digital Interface, is a serial data connection which operates with any make or model of instrument which provides for it. 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 controlled function, such as switching one of the  DSP effects, or the auto-harmony. Keyboard ensemble. In live performances, multiple electronic keyboards could be played together at one time, each by one musician, forming a keyboard ensemble. Keyboard ensembles are mostly performed within a band on an elaborate stage, while some can even serve as a simpler substitute to the more conventional orchestra, replacing stringed and wind instruments.