User Guide

III. MIDI Basics

MIDI stands for “Musical Instrument Digital Interface” and was established over 20 years ago to

give musicians a standard interface for interconnection and control of synthesis gear. Prior to MIDI,

most synthesizer control interconnections were analog CV/gate based, and their standards often

varied from manufacturer to manufacturer. A MIDI connection has standard hardware, as well

as defines a variety of standard digital messages that are sent through a MIDI connection. These

messages are used to define musical events, like notes played, note durations and loudness, or it

can be used to exchange data, such as presets, or even firmware upgrades.

A typical MIDI message consists of a status byte followed by data bytes. A status byte tells the

receiving device what to do with the data bytes that follow the status byte. For instance, a MIDI

Note On message will be followed by a byte that states the Note value to be played, then comes

a byte that tells the receiving device what the Velocity of the Note On is (on keyboards, this is how

fast a note is played, you may associate this with how hard a note is played). Data bytes have 7-

bit values (0-127), though two can be sent together, and by defining one as the Most Significant

Byte, and the other as the Least Significant Byte, 14-bit resolution can be acheived (0-16383).

The MIDI standard categorizes different types of messages into channel messages and system

messages. Channel Messages are for things like Note Ons, and other performance information. A

single MIDI cable can be used to address up to 16 MIDI Channels. MIDI Channels are helpful when

multiple MIDI devices are used, or if a device is Multi-timbral. The Voyager is both monophonic

and mono-timbral, so it operates on a single channel for the purpose of sending or receiving MIDI

data. Here are some important terms for understanding MIDI:

Note On: This tells a synthesizer to start a note event. A Note On message tells the Note Number,

and Velocity information for that note.

Note Off: Follows a Note On message and signals the end of that note. It specifies the Note

Number, and Velocity of Release (on a keyboard, how fast the key is let up). A Note On with a

Velocity of zero is another way to end a note.

Pitch Bend: Tied most often to the Pitch Bend Wheel of a MIDI keyboard, it tells how much that

wheel is pushed up or down. It is up to the synthesizer to turn that into a change in pitch, or other

parameter.

Channel Aftertouch: Some keyboards have sensors underneath the keys to sense how much you

press on the key after you have pushed it down. Channel Aftertouch messages are sent on these

keyboards, and the value depends on how much pressure is applied.

Continuous Controller: The Voyager is a knob-laden synth. Many of its controls provide smooth,

continuous change over their parameters. Continuous Controller messages, often shortened

to “CCs” are used to effect changes in a MIDI synth much as the knobs on an analog synth. A

Continuous Controller message has a CC number, which is assigned to a synthesis parameter

inside the receiving device, and a value from 0-127. The Voyager’s front panel controls transmit

MIDI CCs, and the same parameters can be controlled by MIDI CCs. The Voyager uses a non-

standard implementation of the MIDI CCs, so you should refer to the table on page 53 for a list of

CCs used for the Voyager’s parameters.

System Exclusive: System Exclusive messages are used for sending messages to particular

machines in a MIDI setup, and sharing data that would be irrelevant to other MIDI devices. The

Voyager uses this for sending or receiving its presets, or for updating its operating system.

MIDI Clock: A message used to define a tempo in a MIDI system and syncronize events with that

tempo.