Specifications
Chapter 2: Pro Tools Concepts 11
Core Audio
Apple’s Core Audio provides audio stream con-
nectivity between software applications and audio
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 soft-
ware applications and audio hardware on Win-
dows. Pro Tools software can use audio interfaces
with supported ASIO drivers for playback and re-
cording with up to 32 channels of I/O.
MIDI
MIDI (Musical Instrument Digital Interface) is a
communication protocol for musical instruments.
This industry standard enables connections be-
tween a variety of devices from different manufac-
turers. Examples of MIDI-compatible equipment
include synthesizers, sound modules, drum ma-
chines, MIDI patch bays, effects processors, MIDI
interfaces, MIDI control surfaces, and MIDI se-
quencers.
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 outputs
whatever is received from the IN port. MIDI de-
vices 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 com-
puter over USB or FireWire.
The MIDI protocol provides 16 channels of MIDI
per port. A single MIDI cable can transmit a sepa-
rate set of messages for each of the 16 channels.
These 16 channels can correspond to separate
MIDI devices or to multiple channels within a sin-
gle device (if the device is multitimbral). Each
channel can control a different instrument sound.
For example, bass on channel 1, piano on
channel 2, and drums on channel 10. Similar to a
multitrack tape recorder, a MIDI sequencer can re-
cord complex arrangements—even using only a
single multitimbral 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 con-
nect to and communicate with external MIDI de-
vices.
MIDI Device
Any physical MIDI keyboard, sound
module, effects device, or other equipment that can
send or receive MIDI information.
MIDI signal flow
Not all devices will have all three MIDI ports
(IN, OUT, and THRU).