Roland SC-88 Pro ■About MIDI, MIDI connectors

■About MIDI

MIDI stands for Musical Instrument Digital Interface. MIDI devices can transmit musically related data such as performance data or data to select sounds. Since MIDI is a world-wide standard, musical data can be sent and received between devices even if they are of different types and were made by different manufacturers. In the MIDI standard, data describing a musical performance such as “play a note” or “press the pedal” are transmitted as MIDI messages.

As long as you are using this unit to simply play commercially available music data or to provide sound for game software, it is not necessary to know about MIDI. Simply follow the instructions in the manual for your music data playback device (MIDI player) or your software.

The explanation that follows will help you use MIDI to control this unit in greater detail.

●How MIDI messages are transmitted and received

First we will briefly explain how MIDI messages are transmitted and received.

MIDI connectors

MIDI messages are transmitted and received using three types of connector. Connect MIDI cables to these connectors as appropriate for your setup.

MIDI

THRU OUTIN

	from another MIDI device
to another MIDI device
MIDI IN	: This connector receives messages
	from another MIDI device.
MIDI OUT	: This connector transmits messages
	from this unit.
MIDI THRU	: This connector retransmits the mes-
	sages received at MIDI IN.

*It is possible to use MIDI THRU to connect two or more MIDI devices, but in practice the limit is 5 units. This is because as the signal path becomes longer, the signal deteriorates and the messages can no longer be received correctly.

*On this unit, MIDI THRU and MIDI OUT share the same connector. The MIDI OUT/THRU Select switch (p.136) determines which function the connector will have.

	MIDI
OUT/THRU	IN A	IN B

●MIDI channels and multi-timbral sound modules

MIDI transmits a wide variety of performance data over a single MIDI cable. This is made possible by MIDI channels. MIDI channels allow specific data to be selected out of a large amount of data. The concept is similar to the idea of TV channels. By changing the channel of a TV receiver you can view the programs of different stations. By setting the channel of the receiver to match the channel of the transmitter, you can receive only the program you wish to watch. In the same way, MIDI allows you to receive data only when the channel of the receiver matches the channel of the transmitter.

The cable from the antenna carries the TV signals from many broadcast stations.

Station A

Station B

Station C

The TV is set to the channel of the station you wish to watch.

MIDI uses sixteen channels, numbered 1 — 16. Music data is received when the transmit channel of the transmitting device matches the receive channel of the receiving device. If you make MIDI channel settings as Fig.1, only sound source B will sound when you play the keyboard, and sound source A will not sound. This is because sound source B matches the transmit channel of the keyboard, but sound source A's channel does not match.

Conversely, if you set the transmit channel of the keyboard to match sound source A, sound source A will sound (Fig.2).

MIDI OUTMIDI IN MIDI THRU

	Transmit channel : 1	Receive
	Sound	channel : 2
Fig.1	Module A
		Receive
	MIDI keyboard	channel : 1	MIDI IN
	Sound
	Module B
	MIDI OUT	MIDI IN	MIDI THRU
	Transmit channel : 2	Receive
	Sound	channel : 2
Fig.2	Module A
		Receive
	MIDI keyboard	channel : 1	MIDI IN
	Sound
	Module B

Since this unit has two MIDI IN connectors, it can receive a total of 32 channels simultaneously. By using 32 channels you can play ensembles of 32 Parts (p.23). Sound sources such as this unit which are able to simultaneously play many parts are called multi-timbral sound modules. Timbre is a word meaning sound.

This unit has two types of Parts: Normal Parts and Drum Parts (p.27). Normal Parts are used to play melody or bass lines. On GM/GS sound sources, the Drum Part uses channel 10.

130 Chapter 7. MIDI and the unit