Glossary
Aftertouch
Most modern MIDI keyboards can generate
Aftertouch
messages. If you press down on a key while it is already
playing on such a keyboard, this aftertouch generates MIDI messages. This can be used to add an expressive
volume swell to the sound character (e.g. vibrato).
Control Change (Controllers)
Using these MIDI messages it becomes possible to change the sound response of the sound
generator.
This message basically consists of two parts:
• the controller number which determines what is influenced. It can range between 0 and 120,
• the controller value which determines the intensity of the modification.
Examples of the use of controllers are slowly starting vibrato, movement of the sound in panorama
position or influence on the filter frequency.
Gate
In the field of sound technology the term gate is used in several contexts. The literal meaning shows
you the basic feature of this term: It can be open or closed or, technically speaking, active or inactive.
A gate in the sense of a device is a module which allows a signal to pass or which blocks it, depending
on certain marginal conditions. For example, this is used in a noise gate so that only signals with a
defined minimum level are allowed to pass to suppress the noise in signal pauses. In the context of
analog synthesizers gate is seen as a control signal which can be in either the active or the inactive
mode. An example is the keyboard of such a synthesizer. When you press a key, it provides two
separate signals: CV and gate. The gate signal is active as long as the key is pressed, then it
becomes inactive at once. In sound generation this gate signal may lead to triggering an envelope
which controls the VCA.
MIDI
MIDI is short for ”Musical Instrument Digital Interface“. It was developed in the early eighties to link
electronic musical instruments of different types and from different manufacturers. Up to that time
there was no standard for linking several sound generators and so MIDI was a considerable
improvement. From then on it became possible to link all devices using easy and always identical
connection cables.
The basic steps are: A transmitter is always connected with one or several receivers. If, for example, a
computer is to play a synthesizer the computer is the transmitter and the synthesizer the receiver. For
this purpose all MIDI devices (with only a few exceptions) have two or three connections: MIDI IN,
MIDI OUT and possibly MIDI THRU. The transmitting device provides the information to the outside
world via its MIDI OUT connection. The data are passed on to the MIDI IN connection of the receiver
by means of a cable.
The MIDI THRU connection has a special meaning. It makes it possible for a transmitter to reach
several receivers. It works in such a way that it provides the incoming signal without any changes.
Another receiving device is then simply plugged into the MIDI THRU connector. This process creates
a chain in which one transmitter and several receivers are connected. It is, of course, a requested
feature that the transmitter can control each individual device separately. Therefore it has to be
ensured that the individual devices keep to certain rules among each other.
MIDI Channel
An important part of most messages. A receiving device only reacts to incoming messages if its set
receiving channel is identical with the transmitting channel of the message. This makes clear
information transfer to a receiver possible. The MIDI channel can be selected within the range from 1
to 16. Beyond this range a device can be switched to Omni. Then it will receive on all 16 channels.
MIDI Clock
The time interval of the MIDI Clock message defines the tempo of a musical piece. It is used for
synchronizing time-dependent processes.
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