[noob question] android phone as source

[pereirageomet]

Hi,
Thanks for this amazing solution for multi-room music playing.
I could not figure out if I can use your android app to send the music playing on my phone to all the other clients. Is that possible?
If not, the best I could get is to use the Spotify stream and control the music being played using the Spotify app on my phone?
Appreciate your help!