Chapter 3: Pro Tools Concepts

This chapter explains the principles and concepts that form the foundation of Pro Tools operation and functionality.

Hard Disk Audio Recording

Tape-based recording is a linear medium—you need to rewind or fast forward a tape to hear a particular spot in a recording. To rearrange or repeat material in a linear system, you need to rerecord it.

Hard disk recording is a nonlinear (or random access) medium—you can go immediately to any spot in a recording without having to rewind or fast forward.

Nonlinear systems have several advantages. You can easily rearrange or repeat parts of a recording by making the hard disk read parts of the recording in a different order and/or multiple times. In addition, this re-arrangement is nondestructive , meaning that the original recorded material is not altered.

Pro Tools is a nonlinear recording system that lets you rearrange and mix recorded material nondestructively.

The Digidesign Audio Engine

DAE (or Digidesign Audio Engine) is Digidesign’s real-time operating system for digital recording systems. When you install Pro Tools,

DAE is automatically installed on your system.

In the same way that a computer’s operating system provides the foundation for programs that run on the computer, DAE provides the foundation for much of the hard disk recording, digital signal processing, mix automation, and

MIDI functionality required by Pro Tools and other products from Digidesign and its Development Partners.

The DAE Playback Buffer Size determines the amount of memory allocated within DAE to manage disk buffers, which affects system per-

formance. For more information, see “DAE Playback Buffer Size” on page 40. The DAE Playback

Buffer Size can be changed in the Playback Engine dialog, discussed below.

Chapter 3: Pro Tools Concepts 11

Playback Engine Dialog

Pro Tools takes advantage of your computer’s host processor for certain tasks and optional host-based DSP processing.

Pro Tools LE uses host (CPU) processing to provide audio track recording, playback, mixing, and effects processing. Pro Tools TDM can also use host processing to run RTAS plug-ins for effects processing. Performance is determined by your system and its Playback Engine settings.

The Playback Engine dialog lets you set a hardware buffer size and allocate a percentage of

CPU resources for these tasks. For more informa-

tion, see “Configuring Pro Tools System Settings

(in the Playback System Engine)” on page 37.

Pro Tools Sessions

When you start a project in Pro Tools, you create a session . Some basic elements of sessions are explained in this section.

Session File

Pro Tools session file icon

A s ession file is the document that Pro Tools creates when you start a new project. The session file contains maps of all elements associated with a project, including audio files, MIDI data, and all your edit and mix information. You can make changes to a session and save those changes in a new session file. This lets you create multiple versions of a project or back up your editing and mixing work.

Audio File

When you record audio into a Pro Tools session, audio files are created.

Playback Engine dialog for Pro Tools TDM system

In the Playback Engine dialog, you can also select the number of voices and voiceable tracks for your system and its sessions. Voice count choices in the dialog are based on how much

DSP processing you want to allocate for voicing.

For more information, see “Configuring

Pro Tools System Settings (in the Playback System Engine)” on page 37.

See also “System Resources” on page 16.

The Playback Engine dialog is also where you dedicate DSP resources for Delay Compensation.

Audio file icon

Audio files for each session are stored in a folder named “Audio Files.” Audio files are listed in

Pro Tools’ Audio Regions List and can appear in a track. A section of an audio file can be defined

as a region. See “Regions (or Loops)” on page 13.

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Tracks

Pro Tools tracks are where audio, MIDI, and automation data are recorded and edited.

Playlist

Audio track in the Edit window (stereo track shown)

MIDI track in the Edit window

Audio and MIDI tracks can be edited into regions or repeated in different locations, to create loops, re-arrange sections or entire songs, or to assemble tracks using material from multiple takes.

Audio tracks can be mono, stereo, or any supported multichannel format (depending on your type of Pro Tools system). When creating a new audio track, you can choose from a list of formats supported by your system.

Regions (or Loops)

Audio region

A region (or loop) is a piece of audio or MIDI data that may have associated automation data. A region could be a loop, a guitar riff, a verse of a song, a sound effect, a piece of dialog, or an entire sound file. In Pro Tools, regions are created from audio or MIDI files, and can be arranged in audio and MIDI track playlists.

Playlist Selector pop-up

A playlist is a group of regions arranged on an audio or MIDI track. Tracks have edit playlists and automation playlists .

On audio tracks, an edit playlist tells the hard disk which audio files to read in what order. For example, you can use the same audio region to access the same piece of audio multiple times at different locations and not use additional disk space. Different versions of the same original audio can be used in different places and have different effects applied.

A playlist can be made up of a single region or many separate regions. It can be made up of similar elements, such as regions from several different takes of a solo, or dissimilar elements, such as several sound effects. You can create any number of edit playlists for a track. This lets you assemble different versions of performances or edits on a single audio or MIDI track and choose between them with a pop-up menu on the track.

Each track has a single set of automation playlists, for volume, pan, mute and each automation-enabled control for the insert and send assignments on that track.

Chapter 3: Pro Tools Concepts 13

INPUTS 1-4

SW CTRL GAIN

1 3

2 4

5 7 9

INPUTS 5-16

+4dBu/–12dBV

11 13 15

OUTPUT

+4dBu/–10dBV

1

6 8 10 12 14 16 2

Figure 1. Back view of 96 I/O, with eight analog inputs, eight analog outputs, and eight digital input/output channels

(using a lightpipe)

Channel

The term channel is used to describe several related components of a Pro Tools system. The first example of channel refers to a physical input or output of your Pro Tools system.

For example, a 96 I/O audio interface (Figure 1) provides up to 16 channels of input and output to a Pro Tools|HD system. An 888|24 I/O audio interface provides eight channels of analog input and output to a Pro Tools TDM system.

The second use of the term channel refers to a mixer strip in the Pro Tools Mix window. The term channel strip refers to the mixer strip of any track (audio or MIDI track, Auxiliary Input, or

Master Fader) in a session.

Audio and MIDI channel strips have similar controls, but those controls have slightly different effects. For example, audio and Auxiliary Input channel strip faders control the output gain to the mix bus for that channel, while MIDI channel strip faders send MIDI volume data

(MIDI controller 7) to the MIDI instrument.

Figure 2. Channel strip in the Mix window

The term

channel

also describes a separate

aspect of MIDI operation. See “MIDI Concepts” on page 18.

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Signal Routing

Pro Tools provides software-based mixing and signal routing controls. The Mix window is where these controls are located. (Some of these controls can also be accessed from the Edit window.)

A common signal routing task is to submix multiple tracks to a single channel strip (such as an

Auxiliary Input or a Master Fader) for shared processing and level control. The following example shows three audio tracks submixed to a stereo Auxiliary Input.

Stereo plug-in

Inserts

Sends

Outputs to

Stereo Bus path

Audio Tracks

Submixing to an Auxiliary Input

Input from

Stereo

Bus path

Output to

Stereo Output path

Auxiliary

Input

Signal Routing Options

Signal routing options include the following:

Track Input and Output (I/O) Controls The most basic type of signal routing is track input and output. A track needs to have an assigned input path to record audio, and an assigned output path in order to be audible through a hardware output. Signals can also be routed to or from other tracks in Pro Tools (or hardware inputs and outputs) using internal busses.

Auxiliary Inputs and Master Faders Auxiliary Inputs are tracks that can be used as returns, submixers and bus masters. Master Faders are used as bus and output master level controls. Both

Auxiliary Inputs and Master Faders can have plug-in and/or hardware inserts.

Sends Sends route audio to internal busses to send to other tracks in Pro Tools, or to hardware outputs. Master Faders do not have sends.

Plug-In and Hardware Inserts Software plug-ins and hardware inserts process the audio on their associated track. Plug-in processing occurs completely within the Pro Tools system. Hardware inserts utilize audio interface inputs and outputs, for traditional insert routing to (and from) external effects and other devices.

Paths Pro Tools lets you define any internal or external input, output, bus, or insert with a single name and format (mono, stereo, or multichannel). Paths comprise the lists of available routing choices in track I/O Selectors and other menus. Paths are auto-named by default, but can be customized in the I/O Setup window. See

Chapter 7, “I/O Setup” for more information.

Mixing Formats Sessions can include combinations of mono, stereo, and multichannel format tracks, busses, inputs, outputs, and inserts.

(Multichannel formats are supported on TDM systems only.)

Chapter 3: Pro Tools Concepts 15

System Resources

Track count, plug-in processing, signal path and routing options, and voice availability are ultimately limited by the combined resources available from the host computer, and from your

Pro Tools hardware.

Pro Tools provides several ways to manage and conserve resources to maximize the performance of your system. As you begin working with Pro Tools sessions and tracks, you can take advantage of the following features to extend the effectiveness of your available DSP and other resources:

◆ Pro Tools lets you adjust the performance of your system by changing system settings (such as H/W Buffer Size and CPU Usage) that affect its capacity for processing, playback, and record-

ing. See “Configuring Pro Tools System Settings

(in the Playback System Engine)” on page 37.

◆ Pro Tools allows for session items (such as tracks and inserts) to be manually made inactive, to free up DSP resources. Inactive elements are viewable, editable, and retained within the

session. See “Active and Inactive Items” on page 16.

◆ All Pro Tools TDM and LE systems provide flexible voice options for audio tracks, to help maximize use of available voices in your system.

For more information on voice management

and options, see “Voice Borrowing” on page 102.

Active and Inactive Items

Pro Tools lets you set certain items (such as tracks and inserts) as inactive , in order to free up

DSP resources and mixer connections.

Items in Pro Tools that can be made inactive (or active) include the following:

• Audio tracks, Auxiliary Inputs, and Master

Faders

• Track Inputs and Outputs

• Sends

• Side-chain inputs

• Plug-ins

• Hardware inserts

• Paths (session-wide)

MIDI tracks cannot be made inactive.

In addition to manually setting Active and Inactive modes, Pro Tools will automatically make items inactive if there are insufficient or unavailable resources.

When active , items are fully engaged and operational.

When inactive, items are silent and off, although most associated controls can still be adjusted.

Different inactive items affect available system resources in specific ways, as follows:

Plug-Ins When a plug-in is inactive on a track, its

DSP is made available for other plug-ins and processing. Plug-in assignments can be made in-

active manually, or automatically (see “Automatic and Manual Inactive Mode” on page 17).

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Paths and Path Assignments When a path or path assignment is inactive, its mixer resources are made available for other signal routing purposes in the session. Paths and assignments can be made inactive manually, or automatically

(see “Automatic and Manual Inactive Mode” on page 17).

Tracks When a track is made inactive, its voices become available for another track. Mono inactive tracks free up one voice, and stereo and multichannel tracks free up one voice per channel. Additionally, when an audio track, Auxiliary Input, or Master Fader is made inactive, its plug-ins, inserts, sends, and I/O assignments become inactive, and the associated DSP used is freed up for use elsewhere in the session.

Display of Inactive Items

When items are inactive, their names appear in italics, and their background becomes dark grey.

When a track is inactive, the entire channel strip is grayed out.

Inactive track

Active and inactive items and tracks

Automatic and Manual Inactive Mode

Active and Inactive modes are powerful options for session transfer, and system resource management. Pro Tools provides automatic and manual Inactive mode switching. You can manually make items inactive (or active) to selectively manage system resources while editing and mixing.

Chapter 3: Pro Tools Concepts 17

Automatically Inactive Items

When opening a session, it is possible that not all signal paths, plug-ins, or audio interfaces used in the session will be available as defined on the current system. When opening a session, sufficient voices may also be unavailable if the session was created on a different Pro Tools system type (for example, creating a session on a

Pro Tools|24 MIX-series system, then opening it in on a Pro Tools|HD-series system).

Whenever this occurs, the session will open as it was last saved. All items that are unavailable, or cannot be loaded due to insufficient resources, are made inactive.

Manual Inactive Switching

You can manually apply Active or Inactive modes to manage system resources. By making an item inactive, its associated resources are made available elsewhere in the session.

The following are basic instructions for manually making items inactive. Throughout the

Pro Tools Reference Guide , instructions are provided whenever an item can be made inactive.

To toggle an item active or inactive:

■

Control-Start-click (Windows) or Command-

Control-click (Macintosh) the item.

You can apply Active or Inactive modes to all or all selected tracks using standard Pro Tools modifiers (Alt and Alt+Shift in Windows, Option and

Option+Shift on the Macintosh). Side-chain inputs support direct active and inactive switching, but do not follow switching all or all selected side-chain inputs.

MIDI Concepts

MIDI (Musical Instrument Digital Interface) is a communication protocol for musical instruments. This industry standard enables connections between a variety of devices from different manufacturers. Examples of MIDI-compatible equipment include synthesizers, sound modules, drum machines, patch bays, effects processors, MIDI interfaces, and sequencers.

MIDI devices are equipped with 5-pin DIN connectors, labeled as either IN, OUT, or THRU.

The MIDI OUT port transmits messages; the

MIDI IN port receives messages; and, MIDI

THRU echoes whatever is received from the IN port. MIDI devices are connected with MIDI cables that are available at most music stores.

echoed from IN

MIDI signal flow

Not all devices will have all three MIDI ports (IN, OUT and THRU).

A single MIDI cable can transmit a separate set of messages for each of the 16 channels. These

16 channels correspond to separate MIDI devices or to multiple channels within a single device (if the device is multi-timbral ). Each channel represents a discreet instrument sound; for instance, bass on channel 1, piano on channel 2, and drums on channel 10. Similar to a multitrack tape recorder, a MIDI sequencer can record complex arrangements—even using a single multi-timbral keyboard.

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MIDI Terms

The following are some basic MIDI terms:

MIDI Interface Hardware that lets computers connect to and communicate with MIDI devices.

MIDI Device Any keyboard, sound module, effects device or other equipment that can send or receive MIDI information.

MIDI Controller Any MIDI device that transmits

MIDI performance data. These include keyboards, MIDI guitar controllers, MIDI wind instruments, and others. Controllers transmit

MIDI from their MIDI OUT ports.

MIDI Control Surface Any device (such as the

Digidesign Command|8), which uses a MIDI connection to send control messages to a software program, but is not generally used to record MIDI information.

MIDI Sound Source Any MIDI instrument capable of playing back MIDI-triggered sound.

Sound sources receive MIDI from their MIDI IN ports.

Multi-Timbral The capability of playing several different instrument sounds (such as piano, bass, and drums) simultaneously on separate channels. This makes it possible for a single

MIDI sound source to play back entire arrangements.

MIDI Channel Up to 16 channels of MIDI performance data can be transmitted on a single MIDI cable. The channel number separates the different messages so your sound sources can receive the right ones.

Program Change Event A MIDI command that tells a sound source which of its sounds (or sound patches) to use. The MIDI protocol lets you choose from a range of 128 patches.

Bank Select Message Many devices have more than 128 patches, which are arranged in banks.

The Bank Select Message is a MIDI command that specifies the bank of patches from which to choose.

Local Control A controller setting found on most

MIDI keyboards that lets them play their own sound source. Disabling “local control” ensures that a device’s internal sound source is only played by external MIDI messages.

When using Pro Tools, “local control” should usually be disabled. When “local control” is off, your keyboard still transmits data to its MIDI

OUT port.

Continuous Controller Events MIDI instructions that allow real-time changes to notes that are currently sounding. These include pitch bend, modulation, volume, pan, and many others.

System Exclusive Data MIDI data commonly used for sending and retrieving patch parameter information for storage purposes.

Chapter 3: Pro Tools Concepts 19

Common Misconceptions about

MIDI

MIDI (Musical Instrument Digital Interface) is not audio, and has no sound. The messages that travel down a MIDI cable translate to specific instructions. For instance, when you strike a key on your MIDI keyboard it sends a message to its

MIDI OUT port telling another device (if connected and set to the same MIDI channel) to play that particular note.

Signal paths for MIDI instruments

To actually hear the second device (sound source) you need to connect its audio outputs to a sound system. Your MIDI instruments have two signal paths, one for audio and another for

MIDI.

MIDI does not allow you to use your devices beyond their capabilities. Particular instruments have their own sound generation, polyphony, and multi-timbral limitations.

20 Pro Tools Reference Guide