Hi Con, I found an app called volume control for Android. But i don't have any experiance about it. No doubt it is ripp off. But it sounds good.
https://play.google.com/store/apps/details?id=com.spycorp.appvolumecontrol
I use for myself Samsung Sound Assistent from Samsung galaxy store. It is available for All Samsung smart phones.
Yes, indeed a separate channel would be helpful. At the Moment it works for me very well.
Brian use an interesting seperate solution.
Im fact if you are connected with carplay mra told you all Sound setting Controllers goes over the carplay with all delays we wrote.
Perhaps developer read these thread and offer a solution?
Have a good ride all time
Regards
Westerwald rider