There are two types of channel messages: Voice and Mode.
Commands include playing notes, expressive properties, and monophonic versus polyphonic performing modes.
Channel Voice Messages. Most channel messages are voice message. These commands are the "fingers" that do the playing and require certain data as well as a channel number (1 to 16) to identify the unique channel for broadcasting the data.
The most used MIDI channel voice messages include:
Note On, Program Change (sets the instrument patch), Control Change
Control Change messages (part of the voice message) are messages that can be sent from several different controller devices on a keyboard or other instrument and provide performance control over a variety of expressive properties (Manipulation of wheels, pedals, sliders and other devices).
MIDI Volume - (Controller Message#7) The volume of the MIDI channel > Measured in data values 0 -127.
Modulation Wheel - (Controller Message#1) The mod wheel is used to add expression or to modulate (change) various elements of a synthesized sound or sample).
Velocity - (Channel Voice Message) Is how hard a player strikes a key -Attack & Release. Measured in data values ranging from 0 or (pp-pianissimo) to 127 (ff-fortissimo).
Note On, Note Off - (Channel Voice Message) When a note is played on a MIDI controller a Note On messages is sent along the MIDI cable. When the note is released, a Note Off message is sent.
The pitch of each note is sent as a MIDI Note Number (128 different MIDI note numbers). Middle C= 60, C# above middle C=61, etc.
Panning - (Controller Message#10) Where audio is placed in the stereo spectrum>Left to Right.
Sustain - (Controller Message#64) How long the note is held.
Pitch bend - (Channel Voice Message) Alters the pitch up or down in continuous steps. Two bytes are used and is measured in a range of 16,384 values (-8,191 to 8,191).
Aftertouch - (Channel Voice Message). Additional key pressure. Used to invoke vibrato, increase volume, etc.
There are four combinations of modes:
Omni On means that the MIDI device will respond to all messages that are sent over the 16 channels.
Omni Off means that the MIDI device will only respond to messages over its current channel.
Polyphonic means that the MIDI device is able to produce messages over all 16 channels.
Monophonic means that the MIDI device only produces messages over its current channel.
Mode 3 (Omni off/Polyphonic) is the most frequently used mode for music instruction, sequencing programs and other MIDI compatible devices.
- Omni On
- Omni On
- Omni Off
- Omni Off
Standard MIDI Files (SMF)
Standardized format that allows different sequencers or computer programs to share MIDI data.
SMF’s are similar to RTF (Rich Text Format-Which can be read by almost all word processors).
STANDARD MIDI FILES (SMF)-These files can be loaded into any other sequencer.
SMF’s can be loaded into notation programs and sequencing programs.
3 Types of SMFs.
Format 0 - For exchanging MIDI files in their simplest form especially over the Internet.
Format 1 - For editing MIDI files between multitrack sequencing software where maintaining track distinctions for MIDI data is important.
Format 2 - MIDI data intended to be performed independently, tempo and time signature coded separately in each track; least-used format.
Why have SMF files?
1. Share files over the Internet
2. Exchanging multitrack music between different sequencing software, notation and GM hardware.
3. Most music software and hardware support the MIDI SMF standard.
MIDI And USB
USB-Over the last 10 years the creation of USB and other types of network connections you can purchase MIDI keyboards that don’t require a MIDI interface.
Called USB keyboards-Transfer the MIDi information by way of the USB port. Not an interface.
Many of todays keyboard controllers are USB and MIDI compatible.
MIDI vs. Digital Audio
Sound quality depends on external sources.
Flexible data structure (Ex. Change instrumentation instantly).
Music parts can be separated from the whole.
Small storage demands.
Less-than-perfect reproduction of performance.
Best suited for extended music performance with minimum storage needs.
Sound quality inherent in sampled data.
Inflexible data structure.
Music parts not easily separated from the whole.
Large storage demands (10MB for every minute of uncompressed audio).
Reproduction depends on sampling hardware.
Perfect reproduction of performance.
Best suited for performance where storage is not an issue (DVD-R, CD, External HD).