I might be one of only a few doing something like this, but I listen to my BandHelper Set list MP3's all the time when driving, often to help learn new songs or to stay current on others.
Only drawback is BandHelper doesn't connect with the Car Play transport controls (Apple in my case) for play/pause/skip etc on my car screen like Amazon Music/Apple Music does. Play controls work fine on my Phone/Layout, but not as easy to use as the car screen for sure.
Wasn't going to even ask if that could be considered if there is only a handful of us using it for this - anyone else?
It should work the same way as other audio apps. If BandHelper wasn't the last app you played audio from, you would need to start the playback from BandHelper to make it the target for the remote media controls.
In my app on the Settings > Audio & MIDI page I have Play Audio In Background on and Let Other Apps Play Audio In Background off. I'm not sure if either of those is relevant to this situation, but you could try that combo if you don't have that already.
Also, Settings > Audio & MIDI > Multi-Route Audio could interfere so you could try turning that off if it's on.
Thanks Arlo - I did have "...Let Other Apps Play Audio In Background" turned ON. I turned it OFF and now the play/pause button on the Car Screen does work - thanks!
Cool, good to know.