53
Viscount
Chorum
User Manual
Most instruments equipped with MIDI interface transmit MIDI messages which specify, for example,
which note has been played and with what dynamic, by means of the MIDI OUT connector. If this
connector is connected to the MIDI IN connector of another MIDI instrument, such as an expander, the
second instrument will respond exactly to the notes played on the transmitter instrument.
The same type of information transfer is used for recording MIDI sequences. A computer or a sequencer
can be used to record the MIDI data generated by the transmitter instrument. If these recorded data are
sent back to the instrument, it automatically repeats the recorded performance.
MIDI is able to transmit a multitude of digital data by means of just one cable, and thus just one
connector. this is thanks to the MIDI channels. There are 16 MIDI channels, and in a similar way as for
radio communications in which two stations can only communicate if they are tuned to the same
frequency (or channel), two MIDI instruments connected together are only able to communicate if the
transmitter instrument channel is the same as the receiver instrument channel.
MIDI messages subdivide into channel messages and system messages. The following is a short
description of these messages:
CHANNEL MESSAGES
NOTE ON
This message is transmitted when a note is depressed on the keyboard. Each Note On message contains
the following information:
Note On:
when a key has been struck;
Note Number:
the key which has been pressed, and therefore the relative note played;
Velocity:
note dynamic (i.e. the force applied when the key was struck).
Note messages are expressed as a number from 0 to 127, with middle C represented by number 60.
NOTE OFF
This message is transmitted when a key struck previously is released.
When it is received, the sound of the note relating to the key is switched off. Each Note On message
contains the following information:
Note Off:
a key has been released;
Note Number:
which key has been released;
Velocity:
dynamic (i.e. how fast the note was released).
N.B.:
A Note On message with Velocity=0 is considered equivalent to a Note Off message.
PROGRAM CHANGE
This message is used to select the programs or sounds of the receiver instrument.
There is also a specific standard called General MIDI which describes which sound should be recalled for
each Program Change received. This association is usually described by means of a table included in the
user manual of the instrument which adopts the standard.
This message contains the following information:
Program Change:
voice or program change;
Program Change Number:
the number of the program or voice to be activated;
CONTROL CHANGE
These are control messages (often associated to trimmers or pedals) used to add expression to the
performance, allowing you to set (and control in real time if necessary) voice parameters such as volume
(CC n.7) or the position of the swell pedals (CC n.11), etc.
This message contains the following information:
Control Change:
a controller has been adjusted
Controller Number:
which controller has been adjusted
Controller Position:
the position of the controller
