User`s guide
Pro Tools Reference Guide14
Common Misconceptions about
MIDI
MIDI is not audio. The messages that travel
down a MIDI cable are only numbers that
translate to specific instructions. For in-
stance, when you strike a key on your MIDI
keyboard it sends a message to its MIDI
OUT port telling another device (if con-
nected and set to the same MIDI channel)
to play that particular note.
However, to actually hear that second de-
vice (sound source) you’ll 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 de-
vices beyond their capabilities. Particular
instruments have their own sound genera-
tion, polyphony, and multi-timbral limita-
tions.
Virtual Tracks
(TDM Systems Only)
Tape decks record only physical tracks: they
are limited by the number of tracks on the
deck and on the tape itself. For example, a
16-track recorder can record and play back
a maximum of 16 tracks at a time.
Pro Tools TDM systems are not limited by
the number of physical inputs and outputs.
Pro Tools TDM systems provide up to 128
virtual audio tracks that can be recorded
upon and cued up for playback, but cannot
all be played back simultaneously.
Virtual tracks provide significant advan-
tages: on Pro Tools TDM systems, you can
have many more tracks than voices in a ses-
sion. You can then choose which of these
tracks you want to play, up to the total
number of available voices. You never need
to erase tracks to make room for other
tracks—provided that you have enough
space available on your hard disk to store
all of them. In addition, virtual tracks allow
you to create separate tracks for each audio
component of your mix, each with its own
volume, pan, EQ, effects sends, and auto-
mation.
Pro Tools voices are dynamically allocated.
When a hole opens up in one track, its
voice becomes temporarily available and
another track can pop through and begin
to play. If the first track reaches a point
where audio occurs again, the voice reverts
to the original track. You can determine
the order in which your tracks use available
voices. See “Assigning Voices and Track Pri-
ority” on page 56.
Virtual tracks use the Digital Signal Process-
ing (DSP) capacity of your system. (See
“DSP Allocation” on page 383 for more in-
formation.) Another powerful Pro Tools
feature, multiple edit playlists, allows you to
create comps and alternate arrangements
of material, but does not use additional
DSP capacity. For details about multiple
edit playlists, see “Playlists” on page 141.
Signal paths for MIDI instruments