Mixing different sources (playing simultaneously)


My setup is Volumio (System Version 2.713) on Raspberry Pi 3+ with Hifiberry DAC+ Pro.
I’m using Spotify Connect, and Volumio as a media player for my home automation setup (Home Assistant=HA). HA is running on a different RPI3+ From HA I’m trying to stream mp3-files (Text-To-Speech announcement) to Volumio while Spotify might be playing, so those two streams need to mix together.

My working setup would do this:

  1. Spotify playing at 100% volume
  2. TTS coming to Volumio
  3. Spotify volume down to 50%
  4. TTS announcement mixed together with low-volume Spotify
  5. Spotify back to 100% volume

Currently Spotify is working fine, and so is the mp3/TTS streamed to Volumio… But, whenever I send a mp3-file to Volumio, Spotify will get paused. Volumio is kind of changing the source from Spotify to mp3-player (MPD maybe?). I need the mp3 to play/mix over the Spotify. How I could get this working?

I have same question. Did find a solution?