Note from 26 May 2020

If iTunesMusic plays in the background, there is a media control key in the Touch Bar.

Screenshot of the Touch Bar with media control key highlighted

This key shows the media controls.

Screenshot of the Touch Bar with media controls highlighted

When Music is in focus, there is another Touch Bar.

Screenshot of the Touch Bar with Music app controls highlighted

The control keys and the progress bar are inverted! 🤦‍♂️