Change default Audio app for Airpods?

How do I tell my phone and/or Airpods WHICH audio application to start up when I press the button on the airpod? I have a Samsung phone.

I listen to a lot of audiobooks through Hoopla, but also have a Spotify app. If I'm listening to Hoopla and pause momentarily and then resume, there's no issue.

But if I wait awhile or if I put them back in their case and then on again later and hit the button, it defaults to Spotify. I can't figure out what settings to change to have it default to Hoopla or any other audio app. Thanks for any suggestions.