MX Master programmable button and iTunes
I use a Logitech MX Mouse with programmable buttons (with a program called SetPoint) which I have set up to pause iTunes when I press a certain button on the mouse. It works just fine, until I interact with the other apps. Here's an example scenario that is reproduced every time I do it.
1. Open iTunes, play/pause with mouse works fine
2. Click Up Next, play/pause with mouse still works while the menu is open
3. If I move to another app, the play/pause with the mouse no longer works for iTunes.
Once I reactivate iTunes play/pause works again until I move to another app. However, it's a hassle to have to open and close it, and I'd rather just have a permanent solution so I can go back to pausing with my mouse buttons.