Midi Message Basics; Channel Messages; A Voice Messages - Alesis D4 Reference Manual

machines) can often transmit and/or receive additional MIDI timing messages that
keep other rhythmically-oriented units in a system synchronized with each other.
An optional MIDI Thru jack provides a duplicate of the signal at the MIDI In jack. This
is handy if you want to route MIDI data appearing at one device to another device as
well. Some devices, like the D4, switch their MIDI Out between the Out and Thru
functions.
Example: Suppose a keyboard's MIDI Out feeds the D4's MIDI In. If the D4's MIDI
Out is set to function as a Thru jack, you could patch it to the input of an MMT-8
sequencer. Thus, the keyboard would control the D4 and be able to record data into
the sequencer. Note that any notes generated by the D4 would be recorded into the
sequencer as well.

6.2 MIDI MESSAGE BASICS

The are two main types of MIDI messages. Channel messages, which are channel-
specific, consist of Voice and Mode messages. System messages, which do not
have a channel number and are received by all units in a system, include Common,
Real Time, and Exclusive messages.

6.3 CHANNEL MESSAGES

6.3A Voice Messages

A synthesizer's voice is the most basic unit of sound generation. Usually, each voice
plays one note at a time, so the number of notes you can play at one time will be
limited by the available number of voices. MIDI messages that affect voices include:
Note On Corresponds to a key being pressed down; values range from 000 (lowest
note) to 127 (highest note). Middle C is 60.
Note Off Corresponds to a key being released; values are the same as note on.
Velocity Corresponds to dynamics; values range from 001 (minimum velocity) to
127 (maximum velocity). A velocity of 000 is equivalent to a note-off message.
Pressure Indicates the pressure applied to a keyboard after pressing a key.
Program Change Sending a Program Change command from a sequencer or other
MIDI keyboard can change synth patches automatically. There are 128 Program
Change command numbers.
Also note that not all units number programs consistently. Some number them as
000-127, others as 001-128, and still others arrange programs in banks of 8
programs (such as A1-A8, B1-B8, C1-C8, etc.).
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