Sessions & Tracks : Tracks : Soloing and Muting Tracks : Mute Button

Mute Button
The Mute button silences a chosen track. More than one track can be muted at one time. If Options > Mute Frees Assigned Voice (Pro Tools HD only) is enabled, muting a track will allocate its voice to the next highest priority voiceable track (assigned to the same voice).
To mute a track:
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To unmute a track:
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Mute Frees Assigned Voice
(Pro Tools|HD Systems Only)
Selecting Options > Mute Frees Assigned Voice and muting a track disables playback of that track, and surrenders control of its voice to the next highest priority track with the same voice assignment.
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Muting a track with Mute Frees Assigned Voice enabled does not free up the voice for QuickPunch, TrackPunch, or DestructivePunch recording.
With this option enabled, there may be a delay (ranging in length from one to several seconds depending on the processing power of your system) between the time you mute or unmute a track and when you hear the effect on playback.
MIDI Mute
The Mute button on a MIDI track mutes MIDI data, not audio. Muting MIDI results in no MIDI data being passed to the MIDI output. On Instrument tracks, the track’s Mute button mutes the audio signal and the MIDI Mute button is only available in Instruments view.