Sessions & Tracks : Pro Tools Main Windows : Edit Window : Edit Window Zoom Buttons

Edit Window Zoom Buttons
The Edit window also provides Zoom buttons in the lower right and upper right corners of the tracks pane.
Vertical and Horizontal Zoom In and Out Buttons
In addition to the Zoom controls in the Toolbar, Pro Tools provides horizontal and vertical zoom buttons in the lower-right corner of the Edit window.
 
 
Vertical Zoom Buttons
Zoom the track heights proportionally in the Edit window.
Horizontal Zoom Buttons
Zoom the Timeline just like the Horizontal Zoom controls in the Edit window toolbar.
Audio and MIDI Zoom In and Out Buttons
Pro Tools also provides Audio and MIDI Zoom In and Out buttons in the upper-right corner of the Edit window. These controls function exactly the same as the Audio and MIDI Zoom controls in the Toolbar, and let you zoom in and out vertically on audio waveforms and MIDI notes respectively.
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In the Edit window, MIDI Vertical Zoom only affects tracks not in Clips view.