User Manual

Chapter 2: Pro Tools Concepts 11
Core Audio
Apple’s Core Audio provides audio stream con-
nectivity between software applications and au-
dio hardware on Mac OS X. Pro Tools software
can use audio interfaces with supported Core
Audio drivers for playback and recording with
up to 32 channels of I/O.
ASIO
Steinberg’s Audio Stream Input/Output (ASIO)
provides audio stream connectivity between
software applications and audio hardware on
Windows. Pro Tools software can use audio in-
terfaces with supported ASIO drivers for play-
back and recording with up to 32 channels of
I/O.
MIDI
MIDI (Musical Instrument Digital Interface) is a
communication protocol for musical instru-
ments. This industry standard enables connec-
tions between a variety of devices from different
manufacturers. Examples of MIDI-compatible
equipment include synthesizers, sound mod-
ules, drum machines, MIDI patch bays, effects
processors, MIDI interfaces, MIDI control sur-
faces, and MIDI sequencers.
MIDI devices are equipped with 5-pin DIN con-
nectors, labeled as either IN, OUT, or THRU. The
MIDI OUT port transmits messages. The MIDI
IN port receives messages. The MIDI THRU out-
puts whatever is received from the IN port. MIDI
devices are connected with MIDI cables that are
available at most music stores.
USB and FireWire-compatible MIDI devices send
and receive MIDI messages to and from the
computer over USB or FireWire.
The MIDI protocol provides 16 channels of
MIDI per port. A single MIDI cable can transmit
a separate set of messages for each of the 16
channels. These 16 channels can correspond to
separate MIDI devices or to multiple channels
within a single device (if the device is multitim-
bral). Each channel can control a different in-
strument sound. For example, bass on
channel 1, piano on channel 2, and drums on
channel 10. Similar to a multitrack tape re-
corder, a MIDI sequencer can record complex ar-
rangements—even using only a single multitim-
bral keyboard.
MIDI Terms
The following are some basic MIDI terms:
MIDI Instrument A hardware MIDI device or
software instrument (such as an instrument
plug-in).
MIDI Interface Hardware that lets computers
connect to and communicate with MIDI devices
(such as the M-Audio MIDISPORT).
MIDI signal flow
Not all devices will have all three MIDI
ports (IN, OUT, and THRU).