Just got the car Saturday and I cannot figure out how to have apple CarPlay pause or least lower the music volume enough to hear text messages read out. I have to pause the music every time to hear a text message.
I had a similar imbalance when using Apple Maps. As I recall, the fix was to adjust the volume while the message was being read. That should set things right the next time you get a message.
I tried this, but the audio level for the music still drowns out Siri when a text message is being read.
Hey there, with my experience, Siri does not decrease the volume of other audio sources (spotify and etc). You kind of just have to deal with it for now unless they introduce a software change for it. Cheers!