Global Shortcut Keys and Screen Reader Accessibility?

Hi Folks,
I am looking into the feasibility of global hotkey or Keyboard Shortcut that would toggle a Pause/Play button in a simulated learning environment regardless of where the keyboard focus is currently at in the application.

While the Pause/Play button interaction is somewhat akin to how a video player works, it is not exactly the same kind of experience in our situation.

We are currently working on a science simulation called Molecules and Light <https://phet-dev.colorado.edu/html/molecules-and-light/1.5.0-dev.44/phet/molecules-and-light_en_phet.htm> (note to hear the interactive descriptions you need to use a screen reader - VO & Safari, NVDA & FF or JAWS & Chrome). 

In this simulated environment a learner turns a light source to fire photons at a molecule. The learner can change the light source and the molecule on the fly and observe what happens. 

Learners can also Pause the action (the firing of photons) without turning the light source off. When the action is paused, the learner can use a Step Forward button to move the action (the photons) forward little by little to examine more closely what happens when a photon passes through or is absorbed by the molecule.

In interviews with blind learners, we found that learners were confused by the Pause/Play and Step Forward buttons, especially when the light source had not already been turned on. And if the simulation was set to Pause, they were often temporarily confused why the light source button would no longer fire photons. 

We have made improvements to the descriptive experience by adding aria-live alerts that indicate if the light source is off or if the sim is paused, and why it might be useful to use the Step Forward button when the Pause button is activated. We think these aria-live alerts will create a much more intuitive experience (more user testing is pending).

That said, a few learners requested a global keyboard shortcut to quickly Pause and Play the action no matter where their focus was. My question to the list is, does any one have any experience or resources on making a global keyboard shortcut that does not rely on focus and works when screen reader software is enabled. I am assuming we would need to use a modifier key. Something like Control + k or Alt + k.

This kind of Pause/Play and Step Forward interaction is used in many of our interactive science simulations. A global hot key could be useful for all learners whether they use screen readers or not.

Thanks in advance for any resources on accessible global keyboard shortcuts. I have read this great medium article by Sasha Maximova, J, K, or How to choose keyboard shortcuts for web applications <https://medium.com/@sashika/j-k-or-how-to-choose-keyboard-shortcuts-for-web-applications-a7c3b7b408ee>, several times, and am looking for more resources.

Taliesin
~.~.~
Also available off list at: Taliesin.Smith@colorado.edu
Inclusive Design Researcher
PhET Interactive Simulations
https://phet.colorado.edu/en/accessibility
Physics Department
University of Colorado, Boulder