From Wikipedia, the free encyclopedia
An electronic keyboard or digital
keyboard is a keyboard instrument whose sound is
generated or amplified by one or more electronic
devices.
Electronic keyboards perhaps were most popular in the 1980s, and
are closely related to 1980s pop and New Wave music, but they have remained
popular since.
Internal
architecture
To facilitate the engineering processes of design and
development of electronic keyboards, they are divided into major
components:
- Musical
keyboard: An electro-mechanical component connects the switches
when the key is depressed, which triggers the 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 chip)
which handles user interaction with control keys and menus, which
allows the user to select tones (e.g., piano, organ, flute),
effects (echo or sustain), and other features (e.g.,
transposition)
- Rhythm & chord generator: This part which is again in the
form of software program produces rhythms and chords by the mean of
MIDI 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.
Concepts and definitions
Playing an electronic keyboard.
- Auto accompaniment: Auto accompaniment is used
on programmed styles to trigger specific chords that will sound on
the style.
- Demonstration: Most keyboards have
pre-programmed demo songs 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 of a key
press. 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. The time
between the two 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.
- After-touch: A feature brought in in the late
1980s, 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.
After-touch is found on many 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).
- 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.
- 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. "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.
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 signals 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.
A partial list of
manufacturers
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