MIDI channels

MIDI allows you to independently control two or more devices over a single MIDI cable. This is possi-
ble because MIDI provides for multiple channels of control. You can think of MIDI channels as being
similar to television channels. Although many broadcast channels are in the air at any one time (many
channels of MIDI data are moving through a single cable), a television set receives only the channel to
which it is set (the MIDI device receives only the channel to which it is set).
fig.66
MIDI provides sixteen channels, 1–16, and the receiving device will only receive data when its receive
channel matches the Transmit Channel. In the following diagram, playing the keyboard will cause only
sound module B to play.
fig.67

With the SPD-20, you can set the Transmit Channel (TX CH) for each pad (p. 61). Settings for the

receiving end are made with the Basic Channel (BASIC CH) (p. 67).

Main Types of MIDI Data Used by the SPD-20
A wide variety of musical data can be transmitted by MIDI, with a different type of MIDI message pro-
vided for each type of data. MIDI messages can be broadly categorized into two groups: information
that is differentiated by channel (Channel messages) and information that is not differentiated by chan-
nel (System messages).

Data differentiated by channel (Channel messages)

These messages carry musical performance data. Normally, these messages do most of the work. The
result that each type of message produces will depend on the settings of the sound module.

•

Note messages

These messages notify the sound generator that a pad has been struck. (A keyboard would transmit
these messages when keys are played.) Note messages convey the following information.
Note Number: Each note message (Note On or Note Off) carries the Note Number which was
assigned to that pad (a number indicating the note position on a keyboard).
Note On: This message is transmitted when a pad is struck (when a key is played).
Note Off: This message is transmitted when the specified Gate Time has elapsed after the Note
On message (when a key is released).
Velocity: Each note message contains data indicating how strongly the pad was struck (how
strongly the key was played).
TV Station A
TV Station B
TV Station C
TV messages from various TV Stations are sent through the antenna’s cable.
Select the channel of the TV Station
you wish to watch.
MIDI OUT MIDI IN MIDI THRU
MIDI IN
Transmit channel: 1
Receive channel: 2
Receive channel: 1
Sound Module A
Sound Module B
MEMO
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