Alesis DG8 Manual Do Utilizador

MIDI instruments and devices are connected by a fairly simple system of cables. The

 port transmits data from one device one-way through the cable to the

receiving instrument’s 

. You can setup each device in the system to send and

respond to MIDI commands in a certain way. For example, you can tell a keyboard
or guitar synth to send everything in MIDI except for Program Change commands.
By the same token, you can tell your sound module to respond to any MIDI
command sent to it but ignore Velocity data.

 simply passes data received by 

 right back out to another device

connected to it. This makes “chaining” possible in a MIDI system. For some examples
in connecting MIDI devices together, see our illustrations in the section entitled 

 starting on page 20.

Also of importance in discussing MIDI hardware is the term voice. An instrument’s
voice is the most basic unit of sound generation. It can be an integrated circuit chip
(or chips) or can be a sampled sound in the instrument’s memory, like the DG8.

The are two types of MIDI messages that are communicated through your network
of MIDI cables: Channel and System.

Channel Messages are typically the messages you’ll be most concerned with for
routine MIDI operations and can originate (be transmitted) from virtually any device
in the system. MIDI provides 16 “Channels” through which certain MIDI data is
shared among devices in the system. The communication of certain messages along
Channels makes it possible to connect many devices together but allows you to
specify which devices communicate directly with each other. For example, you
could have seven MIDI devices that are all connected to each other. Two of the
devices can be communicating on Channel 2, two others on Channel 9 and the
remaining three on Channel 4, as one possible setup.

Channel messages are further divided into two groups: Voice messages and Mode
messages. Because these messages are channelized – they are communicated on a
designated Channel number – they are only recognized by instruments that have
been set to receive on that Channel.

System messages, on the other hand, do not have a channel number and can be
received by any device in a system. This permits devices in a MIDI system to share
certain data without having to be set to a particular Channel. System messages, like
Channel messages, can originate from just about any MIDI device in the system. The
three types of System messages are called Real Time messages, Common messages and
Exclusive messages. Because none of these types of messages are implemented on the
DG8, we will not be covering them in this manual.

Each MIDI device is assigned a Basic MIDI Channel. This is the MIDI Channel that the
instrument will use to transmit MIDI data and can be set to any Channel # 1 - 16.
This is also the MIDI Channel that the instrument will receive on.

This principle is not set in concrete, however. For many MIDI instruments, the ability
to communicate – both transmit and receive – on several Channels at once is quite