Published 2023-02-11.
Time to read: 2 minutes.
I am mastering Music In Montreal; the process ultimately becomes an excerise in applying automation to levels. Automation is used whenever the song is played or rendered. Pro Tools documentation refers to the process of rendering audio to a file as bouncing.
When I saw the following video on Pro Tools automation, I felt like jumping for joy. It is terse in the extreme; every word is significant. Not a millisecond is wasted. I played short segments of it back several times to fully grasp the material.
I often curse at Avid’s support and communication style, but features like this really justify relying on their product.
After spending half an hour practicing each editing capability demonstrated in the video, I became comfortable with those features.
Following is a screen shot of my Pro Tools project. Volume automation is applied to two vocal tracks, which are harmonies. Generally, the volume on one vocal track moves in opposition to the volume on the other track; this provides a consistent volume overall. One of the tracks is panned slightly left, while the other is panned slightly right; this improves separation.

Pro Tools Keymap
As ususal for Pro Tools, you must use the numeric keypad’s left‑arrow and right‑arrow keys if you want to slide selected automation nodes forward or backwards.
If you have a smaller keyboard, for example a 10-keyless keyboard, the default keymap does not allow you to move selected nodes in this fashion.
Starting with Pro Tools 2022.4 you can create your own custom keymap. For Windows, type Start+Shift+K to see and modify the keymap. For Mac, type Ctrl+Shift+K instead.
Mute

BTW, while learning I somehow inadvertently added automation to mute, which caused dropouts. That was due to user error, I am sure.
It was easy to delete the mute automation once I realized that it was the problem.
MIDI Volume, Pan, & Mute

MIDI tracks (and their cousins, instrument tracks) have slightly different automation options than audio tracks do. The image to the right shows the automation options for EZ Drummer3, a virtual MIDI instrument.
MIDI tracks rename and repackage volume, pan left, pan right and mute automation, as audio volume, audio pan and audio mute automation, respectively. This unfortunately just adds confusion without providing benefit.
MIDI tracks also provide MIDI volume, MIDI pan and MIDI mute, plus more MIDI-specific automation.
For MIDI channels and MIDI instruments, use audio volume and audio pan for automating the mix.
Some MIDI instruments use sound differently when playing at different volumes. MIDI volume and MIDI pan control the MIDI instrument itself. Most of the time you would not use MIDI volume or MIDI pan, however.