Playing/Pausing iTunes while another app plays media

While browsing on Safari and listening to iTunes I come across a video and then press the "play" button on the keyboard (to stop the music while I watch the video) it starts/stops the video instead of the music (I have no control over the music).

How can I quickly play/pause my music without affecting the video?

If you're not averse to downloading some of the most useful software I've ever installed you can set the play/pause button (on my keyboard fn+F8) to always control iTunes using Karabiner-Elements.

Just add something like the following rule to ~/.config/karabiner/karabiner.json

{  
   "description": "Play/pause button should only control iTunes.",
   "manipulators": [  
      {  
         "from": {  
            "key_code": "f8",
            "modifiers": {  
               "mandatory": [  
                  "fn"
               ]
            }
         },
         "to": [  
            {  
               "shell_command": "osascript -e 'tell application \"iTunes\" to playpause'"
            }
         ],
         "type": "basic"
      }
   ]
}

You may remove the "modifiers" part if you normally press F8 without pressing fn to play/pause iTunes.

Then in Karabiner-Elements you'd add your new rule as a complex modification:

You could just add the iTunes or (since High Sierra) Now Playing widgets to notifications centre:

On a MacBook at least this becomes even easier because the notification centre is just a two-finger swipe away.

In fact, there's even a keyboard shortcut you can set to open up the notifications centre:

1. cmd+tab (switch to iTunes)
2. space (pause or play music)
3. cmd+tab (switch back to App)

Mac Media Key Forwarder allows you to set the media keys to only control either Spotify or iTunes (instead of whichever app you happen to be using).

Base on the @theonlygusti 's answer, I wrote karabiner complex modification rule.

You can find "Media key only control iTunes" group in the https://pqrs.org/osx/karabiner/complex_modifications/

Just import and enable it. (Below capture only shows f8 rules, but soon f7 and f9 rules will be added.)

For more detailed solution, check this link

https://discussions.apple.com/thread/250590543