Overlay Audio Announcement

[DOM5525]

I'm using the Raspberry Pi image for domoticz and I have a USB soundcard plugged into it. The usb soundcard audio jack goes into a speaker system. My desire is to have music playing, either internet radio or music stored on the nas. I have several Z-Wave sensors and I would like to have an audio announcement overlayed onto the current playing music "Garage Side Door Open" through the speakers.

It would be something like this:
Antenne Bayern playing at volume level 80%
Z-Wave device detects garage door open
Antenne Bayern continues playing but the volume is reduced to 40%
Audio announcement plays over Antenne Bayern "Garage Car Door Open" at volume 100%
Antenne Bayern resumes volume at 80%

I have the Z-Wave working fine in Domoticz so that is not the problem. I am using Squeezelite installed on the Domoticz imaged Raspberry Pi, (using these instructions as a base: http://www.gerrelt.nl/RaspberryPi/wordp ... n-raspbian). My issue is the audio overlay. I am able to send commands to the Squeezeplayer to reduce the volume, that works fine. I have installed MPD/MPC and tried to use that to play an mp3 "Garage Door Open" but since Logitech is using the usb soundcard then it is not able to play. "device in use"

So, questions...

Is LMS/Squeezelite my best option for playing the music? My only requirements are internet radio and music files stored on my nas.

How do I get my Domoticz imaged Pi to play multiple audio sources at once, ie Squeezelite and MPD? Is MPD the best option for the overlaying of audio announcements?
I have tried and tried with Pulseaudio, ALSA, dmix and I guess I just don't understand it enough to know what settings to put in what files.

If anyone can help me get this working I would really appreciate it. fyi, I was able to get the MPD controlled using Node-Red since it seems Domoticz doesn't support it that well.

thanks,

[thebeetleuk]

Have you been able to progress with this?