Midi; Midi Channels - Oberheim OB 12 Operating Manual

WHAT MIDI IS
The MIDI (Musical Instrument Digital Interface) allows instruments of different makes and types to
communicate with each other by means of this clearly specified protocol of codes.
This makes it possible to create systems of MIDI instruments offering much greater versatility and
control than would be possible with isolated instruments.
To make this communication possible, all MIDI instruments have two or three 5-pin DIN connectors
called:
- MIDI IN: Connector by means of which the device receives the MIDI data emitted by other
units.
- MIDI OUT: Connector by means of which the device transmits the MIDI data it has generated
to other units.
- MIDI THRU: This connector, used to connect several units in series, emits the MIDI data exactly
as received by the respective MIDI IN port.
For example, most instruments equipped with MIDI interface transmit MIDI messages which specify
which note has been played and with what dynamic through the MIDI OUT connector. If this
connector is connected to the MIDI IN of another MIDI instrument, such as a synthesizer or an
expander, this device will respond precisely to the notes played on the transmitter instrument. This
allows in you in effect to play two instruments at once, and obtain special multi-instrument sounds.
The same type of information transfer is used for recording MIDI sequences. A PC or a sequencer
can be used to record the MIDI data transmitted by the OB-12 or by any other instrument. When
these recorded data are sent to the OB-12, it automatically plays back the recorded performance.
CAUTION! Always use cables of the best quality for the MIDI connections to and from the OB-12. You are also
advised never to use cables more than 5 metres long.

MIDI Channels

MIDI is able to transmit a multitude of digital data by means of a single cable and therefore a single
connector, thanks to the MIDI channels. There are 16 MIDI channels, so the MIDI messages are
processed when the channels of the receiver and transmitter devices correspond. The OB-12 is
able to receive and transmit information on one or four MIDI channels simultaneously (see point
10.1).
Main MIDI messages transmitted and received by the OB-12
MIDI includes various types of messages used to communicate various types of data. MIDI
messages can be subdivided into messages managed separately on each channel and messages
dedicated to the entire system.
The channel messages include:
Note On: this message is transmitted when a note is played, i.e. when a keyboard key is
pressed. Each Note On message includes the following codes:
Note On : when a key was pressed;
Note Number : the key and thus the relative note which has been played;
Velocity : dynamic of the note (the force with which the key was pressed).
Note messages are expressed as a number from 0 to 127, with Middle C represented by the
number 60.
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OB 12