In my car, I use my smartphone SamsungS3 to play my mp3 playlist and the Map Factor audio guidance in the same time (simultaneously).
My smartphone is connected with blue tooth at my car stereo Alpine 185BT and so there is only one channel received by my car stereo with 2 sounds mixed: music and voice Map Factor. So I can't set levels sounds differents for each app which are simultaneously play.
In my case the voice Map Factor is really very very high and is not well to drive. But may be for others users it is the reverse.
My question is: "how adjust the level sound different of each app which simultaneously play?"
If I understand you well my settings are corrects to use custom volume.
Because I don't use TTS voices. It's a good news. : - ))
And now when I use the volume control of my SansungS3 it's seem to me there is a difference. So I'll test this in my car with my car stereo.
But to mix simultaneously this 2 channels when my car is stopped (because it seems to me dangerous to wait an announcement and quickly mix while I'm driving), do you know if there is a test long speech to set up these sounds mixed? (I'm sorry if I'm demanding, but my ears are weakened and very sensitive to the sounds level)