Bluetooth headset for navigation TTS and car Bluetooth stereo for music from same phone

Hi,

I'm trying to get Google maps navigation instructions from my phone to play through my Bluetooth headset while playing music through the car's Bluetooth stereo via Spotify from the same Android phone. This is so passengers don't hear the nav instructions but they may still listen to the music.

I can't seem to separate music from the navigation instructions. They both either play through the car stereo at the same time or both through the headset at the same time.

I've tried to route TTS through the headset as mono but that doesn't work. Only a2dp seems to work with the headset - which is the same 'channel' that the car stereo receives.