Pro Tools 101_ An Introduction to Pro Tools 11 ( PDFDrive )

audio file in that MIDI data does not represent sound waves; instead, it
represents information about a performance, such as the pitch, duration,
volume, and order of notes to be played.
MIDI devices transmit performance data via MIDI messages, which are
composed of 8-bit numbers (or bytes) and include information such as note
or pitch number (indicating an individual note in a scale) and velocity
(typically affecting an individual note’s volume). Up to 16 separate channels
of MIDI information can be sent over a single MIDI cable, allowing a single
cable path to control multiple MIDI devices or to control a single device that
is capable of multi-channel (or multi-timbral) operation.
The Format of a MIDI Message
The most significant bit of a MIDI message byte is reserved to distinguish
between status bytes and data bytes. The remaining seven bits represent the
unique data of the message byte, encompassing a range of values from 0 to
127. The maximum length for a standard MIDI message is three bytes,
consisting of one status byte and one or more data bytes.
Status Byte Data Byte 1 Data Byte 2
1tttnnnn 0xxxxxxx 0xxxxxxx
Where:
t is used to specify the type of status message being sent
n is used to specify the associated MIDI Channel Number
x is used to specify the associated data value, such as a note number (pitch)
or velocity value
Many other kinds of information can be conveyed via MIDI messages, such
as pan and general MIDI volume information for instruments that support
these, as well as program change events, or commands that tell MIDI
instruments which of their available sounds, or patches, to use.
A MIDI sequencer allows you to store, edit, and play back MIDI information
that can be used to control MIDI-compatible devices, such as synthesizers,
sound modules, and drum machines. These devices don’t have to be external
hardware devices—today many software synthesis and sampling packages
are available, enabling you to add internal devices to your host computer.