Some Notes On Midi; Midi Channel - Marshall Amplification JMP-1 Handbook

Some Notes On MIDI

In a modern guitar set-up you might have a number of elements, a pre-amp and an effects processor or
two. By using MIDI to link these devices together, you can control them all simultaneously. This is the real
use of MIDI for the guitarist (Musical Instrument Digital Interface). Most MIDI devices are equipped with
three MIDI terminals, MIDI IN, MIDI THRU and MIDI OUT. The connection between these terminals is quite
simple. A MIDI IN terminal would be connected to a MIDI Out or MIDI THRU terminal. Messages are sent
from a MIDI OUT terminal to a MIDI IN terminal.
MIDI messages received at the MIDI IN terminal are simultaneously routed through at the MIDI THRU
terminal. So the messages being sent via MIDI THRU are a direct copy of the messages received at
MIDI IN. The MIDI OUT terminal is not the same as the MIDI THRU terminal. The JMP-1 will send it's own
MIDI messages via the MIDI OUT terminal.
There are various different MIDI messages that one device can send to another. The most important
message is the MIDI program (patch) change message. When the JMP-1 receives a program change
message it will call up a patch. Whenever the JMP-1 calls up a new patch it also sends a MIDI program
change message via the MIDI OUT terminal. Pressing a pedal on a MIDI foot controller will send a
MIDI program change message. Each MIDI program change message carries a number between 00 and
127 corresponding to the patch/program to be called up. The JMP-1 has 100 internal patches but will
respond to all 128 MIDI program change messages, by using a MIDI mapping table.

MIDI Channel

Another important thing to know about MIDI, is the idea of MIDI Channels. Most MIDI messages are sent
over a MIDI Channel, of which there are 16. In order for one MIDI device to communicate with another,
both devices must be operating on the same MIDI Channel.
The JMP-1 can be set to operate on any one of the 16 MIDI channels or in Omni mode. In Omni mode the
JMP-1 will respond to MIDI messages on all channels and will transmit on channel 1.
To Set The MIDI Channel: After pressing the channel key the display will indicate the current MIDI Channel
setting (Fig 4).
Fig 4 Channel selection
Patch
Patch
Data
Store
Use the data entry control to select channels 1 to 16 or Omni
mode. Press the channel key again to store the channel setting
and return to patch mode.
Note: The MIDI Channel setting is a 'Global` parameter and not
stored with an individual patch. MIDI Channel setting is retained
whilst the unit is not powered.
8